When you pick up you hear a dial tone, when you dial a digit the dial tone quits, but the call never completes?

(If the dial tone doesn't quit when you push the first digit, that's indicates something different)

Did your region recently change to 10 digit dialing?  (If you don't know, what's your area code)?

How long are you waiting for it to start ringing/busy whatever?

What kind of phone service do you have, VOIP or POTS or ...?

Do you have another phone that you can plug in to the jack instead of this phone and see if it also has the problem?

(My gut is telling me that the problem has nothing to do with the phone, but with the service. )

If you have digital service from the cable company or another carrier where the phone plugs into a modem try resetting the modem. As stated by @JefferMC sounds like a carrier or a modem issue. The type of service you have would help. 

I have VOIP. I have an Ooma device that connects through my internet.

Reset the Ooma ATA. When you push a button does the dial tone go away or continue? You can also try another phone, as suggested. I doubt very much it's the phone.