Last couple of days the land line phone hasn't worked. Oddly enought immediately after a new furnace and A/C were installed. No phone jacks work but the jack on the back of the router/modem does work. Rebooted router also. Is this an issue in the house and not comcast?
If the phone jacks on your combo modem-router gateway work but the ones in your home don't, that means there's a wiring problem in your home. If you are unable to find the problem you might want to have an electrician who specializes in low voltage wiring take a look at the problem.