Our phone is not working. We cannot get a dial tone.

try changing phone to tone dialing . one phone line has been setup for Decadic dialing and the other line may be setup for tone dialing.
If tone dialing is working on one line but not the other then get phone company to change the dialing type on the phone line.
Dual tone multi frequency is the technical name for tone dialing and is more efficient than decadic dialing or pulse dialing.

I want to make sure I understand this completely. You get no dial tone from the fax machine when hooked up to VOIP. In the past, was there an audible dial tone from the fax, or did it just dial silently and give you an error if there was no tone? When you said you got a dial tone by connecting a phone to the ext phone port of "the machine" did you mean the fax machine? If you get a dial tone by running a phone through the fax machine, then the line is good. I have used a fax machine over Sunrocket before they went defunct, which used the same technology base as Vonage - so it should work. If you used to get an audible dial tone when using the fax, and no longer do, and you are geting a dial tone on a regular phone that is connected to the ext. port of the fax machine, then the problem has to be in the fax machine itself, not the VOIP. If you can verify that, we can go from there.

Just press top left (R/<-) button about 3 sec. and a letter changes (p - pulse or t - tone).

I would contact your phone provider. It could be a coinceidence that the dial tone stopped working.
DSL does not require dial tone to work.

Headset says ringer off, cannot hear dial tone

That isn't a whole lot to work with. Get a working phone and take the cord out of the base of the GE and plug it into the working phone.
If the working phone gets a dial tone, look into the modular receptical on the GE base and see if the contact wires aren't out of place.
If you don't get a dial tone on the working phone, try changing the connection cord between the phone and the wall. Also look for the same problem in the wall receptical as discribed above for the GE base.

The Vetech phone will only support tone dialing. It does have a menu option that turns tone on or off but it still will not allow pulse dialing. I had to change the phone service from pulse dialing to tone dialing to get the phones to work. As it turned out, the phone company no longer charges extra for the tone service.

The problem is possibly the keypad on the phone. Try another phone , preferrably a standard corded phone. If you still cannot break the dial tone, then the problem is with the telephone line (phone company)

Lisa, If the 900MHZ phone is Model 26928M programming for rotary dial usually goes like below, can't hurt to try on any model. TONE/PULSE DIALING This adjustment allows you to select tone (touch-tone) or pulse (rotary) mode dialing. The phone is pre-set for touch-tone use. To set to tone or pulse dialing: 1. Press and hold the program button for two seconds. You will hear a beep. 2. Press the *tone button to select Tone Dialing or press #pause to select Pulse Dialing. 3. Press the program button again. You will hear a confirmation tone.

Make sure your phone is in Tone and not Pulse dialing. To change it for your phone, just look in your manual. If you don't have one, I have included a link for you to d/l it.

Manual