Sorry you are having trouble.
Can you reset the modem by using a toothpick or aballpointpento reach in to the small hole on the back of the modem to depress the reset switch? Hole the switch in gently until the lights go out , all except the power light , and then release and see if that helps.
Also try plubbing a wired phone in the L1 jack on the back of the modem to rule out house wiring issues.
When i plug in telephone in to modem phone work but when i plug the modem in to the wall as the was and phone in to next room to the wall jack the phone is dead. I try all the jacks in the house.
I have had the same problem. It has happened 4 times over the last several months. I called Comcast support, but the problem continued. I had the inside wiring checked and no problem was found. Each time the problem went away by itself. It happened last night. I touched nothing, did nothing. 12 hours later, everything was working. So far, nobody has been able to provide an answer.