Why doesn't my hp laserjet pro 400 m475dw fax distinctive ring not answer.

There is excellent support here on basic fax setups. You have what is known as "Distinctive Ringing Service". There are pros and cons to the various setups. I assume you recognize the rings and answer only when the ring for the landline talk comes on. The fax will pick up the faxes, and the answering machine will pick up the voice.

Need model number of your fax - google that!

Service manual for your phone.

http://service.us.panasonic.com/OPERMANPDF/KXTG7841-MUL.PDF
This link shows various configurations of setting up your phone/fax/answering machine or using an answering service.
http://h10025.www1.hp.com/ewfrf/wc/document?cc=us&lc=en&docname=c00059780#Dist_ring
Distinctive Ringing Service setup While it is not available everywhere, a distinctive ringing service can be purchased from most telephone companies. With this service, more than one phone number is assigned to the same phone line. Each phone number will ring differently. The main number will ring with a normal single ring and the additional number will ring with a distinctive ring pattern assigned by the phone company.
When a distinctive ringing service is used, set the Rings to Answer to 2 and then follow the steps below to set the distinctive ringing pattern:

1. Press Setup , press 4 , and then press 1 to enter the Answer Ring Pattern setup of the Advanced Fax settings.
2. Use the Right Arrow to scroll through the available settings. When the ring pattern assigned by the phone company displays (double or triple rings), press OK .

Try resetting the machine to it's defualt settings.

If I'm getting this right, your printer says "Device is busy, Try again later" when you try to Scan to Email ? Make sure your Scan to email-configuration is set up correct. Still no luck ? Leave the printer without power for 30 min. You can also try a factory reset. If nothing help, check if your printer is still under warranty HERE. If still warranty call your local HP support and ask for service.

Was the fax plugged into another telephone line? Maybe a power surge?

My solution would be to reconfigure the fax from scratch to learn the ring pattern.

From the Manual:

Step 1-Teach the HP Fax the ring pattern

The HP Fax will learn the ring pattern when you call it from another telephone or fax
machine.

1. Be ready to call the fax machine.
2. Press Menu repeatedly until BASIC FAX displays and press OK.
3. Use LEFT ARROW - RIGHT ARROW BUTTONS to scroll through the options until DRPD Mode displays and press OK.
Call this fax from another fax machine... Waiting Ring...
will display.
4. Call the HP Fax.

DRPD OK will display when the pattern has been learned and the HP Fax will return
to Ready mode.

Step 2-Set up distinctive ring (DRPD) answer mode

Once you have activated distinctive ring, it becomes one of the answering modes you
can select by pressing the Mode/Contrast button.

Press Mode/Contrast repeatedly until DRPD Mode appears in the display.

• In Ready mode, DRPD appears in the right hand corner of the display.
• Now, the HP Fax will manage calls and faxes as if it were set to AUTO mode
(AUTO mode on page 28)


TIP: Distinctive ring must be set up again if you reassign your fax number
or connect the machine to another telephone line. Once set up again (that
is, the fax machine has learned the ring pattern and the answering mode is
correctly set), you should test the fax machine by calling the fax number
and another number on the same line. The machine should respond
appropriately to a call placed to the fax number with fax tones, and to a
normal telephone call with the expected ring pattern.

Distinctive Ring basicsDistinctive Ring service is an optional service available from many telephone companies. The Distinctive Ring service permits you to assign more than one telephone number to the same telephone line. Distinctive Ring allows you to use a single phone line for both voice and fax calls. You can assign a unique phone number and ring pattern for incoming fax calls. When a fax comes in, each telephone number makes a distinctive ringing sound, such as a single ring, double ring, or triple ring.
NOTE: The Distinctive Ring Service is the name HP and others use to describe this feature. Distinctive Ring is also known as:

• Call Sign
• Custom Ring
• Ident-a-Call
• Ident-a-Ring
• Ident-a-Ring
• Multi Ring
• Personalized Ringing
• Ringmaster
• Smart Ring
• Teen-Ring

The Distinctive Ring Service allows the HP product to work similarly to a dedicated fax line. If you connect an HP fax product and a telephone to one telephone line, you can assign one telephone number for fax calls and another for voice calls.
NOTE: You cannot send or receive faxes when the phone line is in use. Even if the HP fax product has a separate telephone number, it is still sharing the same phone line. Set the Distinctive Ring Service Using the menus on the product control panel, follow these steps to set a distinctive ring pattern. Step one: Turn on Auto Answer Turn on Auto Answer by pressing the Auto Answer button on the control panel. The button light indicates when Auto Answer is on.If the button light is already on, you do not need to press the button. Step two: Set the distinctive ring patternFollow these steps to change the answer ring pattern.

1. Press the Setup button ( ) on the product control panel.
2. Press the Right Arrow button ( ) to select Advanced Fax Setup , and then press the OK button.
3. Press the Right Arrow button ( ) to select Distinctive Ring , and then press the OK button.
4. Press the Right Arrow button ( ) to select one of the following options:
   • All Rings
   • Single Rings
   • Double Rings
   • Triple Rings
   • Double & Triple Rings
5. Press the OK button to select the option.
6. Press the Back button ( ) to return to the main menu.

Now if you have anymore problems copy the link from below and paste it in your address bar and it will help you further with a document. Follow all the settings in the document and your fax should be setup,keep in MIND THAT THE RINGS TO ANSWER SHOULD BE 2,SO YOU CAN RECEIVE FAXES AFTER TWO RINGS

http://h10025.www1.hp.com/ewfrf/wc/document?docname=c01647469&tmp_task=solveCategory&lc=en&dlc=en&cc=us&lang=en&product=3795406

Firstly, you will need to get a 2nd ringtone from your phone provider. Most of them will provide a designated "fax ring" (not a new number) for little or no cost.

In DRPD mode, you can receive a call using the Distinctive Ring Pattern Detection (DRPD) feature. “Distinctive Ring” is a telephone company service which enables a user to use a single telephone line to answer several different services.

Using the Distinctive Ring Pattern Detection feature, your fax machine can “learn” the ring pattern you designate to be answered by the fax machine. Unless you change it, this ringing pattern will continue to be recognized and answered as a fax call, and all other ringing patterns will be forwarded to the
extension telephone or answering machine plugged into the EXT. jack. You can easily suspend or change Distinctive Ring
Pattern Detection at any time.

Before using the Distinctive Ring Pattern Detection option, Distinctive Ring service must be installed on your telephone line by the telephone company. To set up Distinctive Ring Pattern Detection, you will need access to another telephone or someone available to dial your fax number from outside (a cell phone will do!).

To set up the DRPD mode:

1 Press Menu until “Fax Setup” appears on the top line of the display.
2 Press the scroll button ( or ) until you see “Receive Mode” on the bottom line and press Enter.
3 Press the scroll button ( or ) until you see “DRPD Mode” on the bottom line and press Enter.
4 When “Set” displays on the bottom line, press Enter.
“Waiting Ring” appears on the display.
5 Call your fax number from another telephone. It is not necessary to place the call from a fax machine.
6 When your machine begins to ring, do not answer the call.
The machine requires several rings to learn the pattern.
When the machine completes learning, the LCD displays “End DRPD Setup”.
If the DRPD setup fails, “DRPD Ring Error” appears. Press Enter when “DRPD Mode” displays and retry from step 3.
7 To return to Standby mode, press Stop/Clear.
When the DRPD feature is set up, the DRPD option is available in the Receive Mode menu.

To receive faxes in the DRPD mode,
you need to set the menu to DRPD;

NOTES:
• DRPD must be set up again if you re-assign your fax number, or connect the machine to another telephone line.

• After DRPD has been set up, call your fax number again to verify that the machine answers with a fax tone. Then have
a call placed to a different number assigned to that same line to be sure the call is forwarded to the extension telephone or answering machine plugged into the EXT. jack.

• In Tel mode, you can receive a fax by picking up the handset of the extension phone and then pressing the remote receive code Alternatively, you can press On Hook
Dial (you can hear a fax tone from the remote machine) and then press Start on the control panel of your machine.
• In the Fax mode, the machine answers an
incoming call and immediately goes into fax
reception mode.
• In Ans/Fax mode, the answering machine answers an incoming call, and the caller can leave a message on the answering machine. If the fax machine senses a fax tone on the line, the call automatically switches to Fax mode.
• In DRPD mode, you can receive a call using the Distinctive Ring Pattern Detection (DRPD) feature. This option is available only when you set up the DRPD Mode.

The full user manual for your machine is located here

Hope that is of help to you :)

You can add more rings to answer, but the only real way is to get distinctive ring from your phone co. or a separate line for fax. When you change the setting to manual receive, you have to answer yourself and if you hear fax tones you hang up and press fax start, or receive.

The following set up assumes you have one conventional phone line, but two different phone numbers. One being your regular phone number and the other a distinctive ring for your fax machine

If that is what you have then this is how you set up the phone. Its important to know what type of distinctive ring your phone company will send to your phone. If it doesn't work you can talk to them about getting a different one than their default distinctive ring.

2 Set the HP all-in-one to answer incoming calls automatically.

Press the Auto Answer button until the light is on.

3 Change the Answer Ring Pattern setting to the pattern that has been assigned to your fax number by the telephone company, for example, double rings or triple rings.
For information on changing this setting, see Change the answer ring pattern
(distinctive ringing).
Note Your HP all-in-one is factory-set to answer all ring patterns. If you do not set the correct ring pattern assigned to your fax number by the telephone company, your HP all-in-one might answer both voice calls and fax calls or it might not answer at all.

4 (Optional) Change the Rings to Answer setting to one ring or two rings.

For information on changing this setting, see Set the number of rings before answering.
5 Run a fax test. For information, see Test your fax setup.
Your HP all-in-one will automatically answer incoming calls that have the ring pattern you selected (Answer Ring Pattern setting) after the number of rings you selected (Rings to Answer setting). Then it will begin emitting fax reception tones to the sending
fax machine and receive the fax.


If it is easier or you want to know other options which may be more applicable to your phone setup. You can find that information here.

http://h10032.www1.hp.com/ctg/Manual/c00235090.pdf

It's either your phone, or it's your fax machine that does not support fax through phone.

here is the manual look for chapter 6 page 104

http://www.retrevo.com/search/v2/jsp/downloadPage.jsp?doc=ab7afe965f3f13c1eb17fc47e69d8294&q=Brother+FAX-2820