Fax failed due to error at dialing - Konica Minolta bizhub C351 All-In-One Laser Printer

If you get issues like Faxes can be sent but not received, Faxes can be received but not sent error on your Printer then follow the given troubleshooting steps.
Solution to Faxes can be sent but not received

·Initially, you have to check any of the telephone line services are enabled. There are,
1.Voice Mail
2.Call Waiting
3.Billing Tone
4.Privacy Block
5.Security Screen
6.Anonymous Call Rejection
7.Privacy Manager
·These may block your incoming faxes. So disable the above features.
·If you are using Automatic fax reception option on your fax recipient, then check whether the Automatic Answering feature is enabled or not, if it enables means Auto Answer green LED should be on.
·Check the Ring to Answer value.
·If the value set as answering machine that causes the issue on fax reception. Then change the value to Fax or FaxTel
·Now, you can receive the incoming faxes.
Solution to Faxes can be received but not sent

·Check whether the dialed number is correct or not. Every one of the digits required to make a telephone call from a similar line must be dialed.
·On the off chance that the Speed Dial has been used for dialing or the fax has been sent from your PC, print the page to be faxed and dial the number physically on the HP Fax front board.
·Check whether the Tone Dialing is set on you HP Fax product.
·In the event that faxes are sent effectively from the HP Fax front board, but, it's fail when sent from the PC, test the communication between the HP Officejet 4650 printer and your PC by tapping the Status button in the HP Director application, or attempting to print some record.
·If the printing fails to send the fax, then check whether all cables (from system to HP Officejet 4650 Printer) are connected properly, if it's not then connect it properly.
·Now restart it. On the off chance that communication still can't be set up, Call Printer customer service team via Toll-Free: +1-800-836-3987 to resolve your HP Officejet 4650 fax issues.

A manual for this unit is available here.

Hi,

Are you able to send fax to another # ?. Error 420 & Error 321 is mainly due to transmission of signals or incompatibility issue.

Try reducing Fax speed and turn off ECM from Fax menu and check.

Regards,
Sean

First I would plug a regular phone into the phone line to make sure it has a dial tone. Assuming that works send a fax to your cell phone and see if the fax machine dials out and makes your cell ring. Assuming that works check the fax for an error code as to why it is not faxing or failing.

The remote machine has failed to respond to a fax command from the local machine due to the connection being interrupted.

Number of possible causes, check the phone line, try a different fax number for a start. Is there other fax machines in the office on the same line

Check the phone line with a regular phone and listen for a dial-tone.

First, check your fax's phone line. Put a regular phone on it and check for dial tone and line noise. If the line is dead or noisy, this will cause a problem. 
You can also try dialing your fax number from another phone and see if the fax unit picks up the line and starts initiating communication. (sounds like modem noises)

Check the line for a dial tone on the machine. Either the handset, onhook or speaker phone button. This will test if any comunictions boards have failed in the machine. If you have a dial tone the fax is ok

Next try a manual transmission. Basically make a normal phone call with for example using the handset but have your original in the fax ready to go, ring the fax number when you hear the other fax pick up you press the start button.

Don't forget the other fax may have a problem.

As some fax machines are not capable of receiving color faxes, legal size faxes, or faxes at 200x200 dpi resolution, make sure you are sending an A4 or letter size (not legal size) page at standard resolution:
Press the Black button for a black-and-white fax. Press the Quality button to check the selected resolution.
Make sure the All-In-One has enough memory free when you want to save the scanned documents into memory before sending the fax. Please refer to the following document: Click here to link to the relevant document.
Note: The scanned documents will only be saved in the memory before the whole fax is sent if the Scan Before Dial option is turned on. (This is the factory default.) Up to 50 black-and-white fax pages can be stored in memory at standard resolution when there are no pending faxes in the queue.
Turn off the Scan Before Dial option by pressing the following keys on the operator panel:
Press the Fax button, then press Options 15 times to get to ADVANCED FAX mode.
Press Select.
Press Options nine times until SCAN BEFORE DIAL appears on the LCD display.
Change the setting from Yes to No using the + (right arrow) button.
Press Select.
Note: The Scan Before Dial option controls whether a document is scanned before a call is dialed. This parameter only applies to a mono fax that uses either 200x100 or 200x200 resolution. Higher resolution mono faxes and all color faxes are scanned after the call is dialed and the receiving machine's capabilities are known.
Lower the fax transmission speed to 14400 or even 9600 bps, as some older fax machines are not capable of receiving a fax at a high speed. To do so:
Press the Fax button, then press Options 15 times to get to ADVANCED FAX.
Press Select.
Press Options 10 times until MAX SEND SPEED appears on the LCD display.
Change it to 9600 BPS using the - (left arrow) button.
Press Select.
Turn off ECM (Error Correction Mode) by pressing the following keys on the operator panel:
Press the Fax button, then press Options 15 times to get to ADVANCED FAX.
Press Select.
Press Options 11 times until ERROR CORRECTION appears on the LCD display.
Change the setting from On to Off using the + (right arrow) button.
Press Select.
Note: Turning off this option makes it possible to receive a fax when the receiver fax machine does not support certain error correction modes. The X6100 Series only supports 1-D MH encoding with the error correction. Fax transmissions without ECM and other ECM types can result in bad quality on the received page.

HP Officejet 7210 All-In-One InkJet Printer
Error code: 405

When I send a fax I have a dial tone and the fax feeds through, I hear the other end answer it says it is sending and then I get the printed page that says: "A communication error occurred during the fax transmission."