It wont connect

If you have another phone connect it to the wall outlet to see if you get a dial tone. This will indicate if your base unit is faulty.
Check the power adapter to the base unit, make sure it is getting mains power.
If the base unit has dual phone lines and if line 1 is only connected and the line 2 has beed selected then you cannot get a dial tone. In the chase press the line 1 to get a dial tone.
If your base unit has only one line then check the phone line at the wall socket make sure it is plugged in tight, also check the the connection at the base unit.
If this does not work then ring the phone company and get the to test your phone line, you may have a faulty line to your home.

Resetting the voice message waiting indicator
When you receive a new voice mail message, the new message LED on the top of the handset flashes. In the event your message waiting light gets out of sync with your phone company's
voice messaging system, you can manually reset it back to the "No messages waiting" state.
1. Press and hold FiND on the base for five seconds.
Note: The handsets connected to the base will start to beep, however, keep pressing for five seconds.
2. A beep sounds and the message alert tone is reset.
Changing the dial mode
Your phone can communicate with the telephone network in two different ways: tone dialing or pulse dialing. These days, most base networks use a method called tone dialing, so your phone comes programmed for tone dialing. If your phone company uses pulse dialing, you will need to change your phone's dial mode. If you don't get a dial tone or can't connect to the telephone network, please follow the steps below to modify your phone's settings:
1. Press MENU/SELECT.
2. Select the Global Setup menu, and then the Dial Mode submenu.
3. Scroll to highlight Pulse.
4. Press MENU/SELECT. You will hear a confirmation tone.
If you ever need to change the dial mode back to tone dialing, follow the same procedure, but select Tone in step 3.

Finally for future ease of use, here is a link to the user manual were I copied the above information from:

http://www.uniden.com/content/ebiz/uniden/resources/ownersmanuals/DECT1580-3om.pdf

Which make and model of phone is it?
Are you pressing the green call button beforew you try to enter the number you are calling?
You should enter the number first, then press 'green'
You wont hear a dial-tone like a landline phone

hello
first you connect the telephone port to your machine and telephoe line.
.then load your fax document to ADF. then their is a button in your machine its name ON HOOK DIAL .press it then you can here some dial tone. press fax number if you wont to send. then you can here some ringing tone and press start button after fax tone coming.

The battery in the handset could be bad . First I would test that the base unit is recieving dial tone by pressing speaker button on base unit. If there is dial tone then problem is in handset or in base unit communication to handset. Try resetting power to base unit. Check manual for any re-initialization procedure. If the base unit is not receiving dial tone then I would test that the phone line is delivering dial tone to the base unit by connecting a known good phone to the line cord. If the dial tone is not present , problem could be in line cord from outlet, outlet, building wiring, or service provider.

Here's what the manual says: Changing the Dial Mode (Tone or Pulse Dialing) (HS1 only) Your phone can communicate with the telephone network in two different ways: tone dialing or pulse dialing. These days, most phone networks use a method called tone dialing, so your phone comes programmed for tone dialing. If your phone company uses pulse dialing, you need to change your phone's dial mode. If you don't get a dial tone or can't connect to the telephone network, follow the steps below to modify your phone?s settings: With the phone in standby, press and hold [cid/menu]. Press [vol/ / ] to move the pointer to select DIAL. Press [select/channel] to set the phone to pulse dialing. Press [end]. Return the handset to the base. The handset communicates the new setting to the base, and the base activates the setting on any other handsets. Hope this helps out. K

Generally this is an indication of a modem failure. If there have been any storms in your area, then the modem may have been zapped. The dial tone curcuit is normally the first casualty when a modem gets hit with more power than normal.

Provided that your telephone is functional on that line (Unplug modem, and connect a handset if this is a modem only line and see if the handset gets a dial tone, this is a good check to make sure the line is functional)

1) When the phone is in standby mode, press and hold the caller id/menu key.
2) Press the vol/ / key three times to select Dial.
3) Press the select key to toggle between Tone and Pulse.
4) Press the end key or return the handset to the base unit to complete the setting. The handset returns to standby mode.

This phone also has a feature that allows you to use Pulse dialing to make calls, but allows you to switch to tone dialing for automated systems (like “Please Press 1 for English) here are the steps for that:

Initially make your call with the pulse dialing mode. Once your call connects, press
the */tone key. Enter the desired number. These digits will be sent as tone dialing.
Once the call ends, the tone mode is canceled and pulse dialing mode resumes.

Have You Tried Replacing The Cable Connecting the Base To the Wall Jack? If Not Do That...
If that doesnt work there should be a channel button on the handset try that...If that doesnt work i would say the handset itself is bad.

talk with a technician about a problem phone line filter for the internet
it is possible that it has failed and the adsl and phone frequencies are giving a problem to the phone operation