Hi, we've had this problem twice already and we're wondering if others might have (had) the same issue and/or some insights about it. (We have FIOS.)
One day we didn't have a dial tone anymore on any of our lines inside the house. DId the on-line trouble shooting first, which didn't come up with any problem on Verizon's end. Then I went to check the NID to see if there is a dial tone there. There was, so I figured that something must have gone wrong with the internal phone lines to the phone jacks and that we would be on the hook for fixing that. However, when I then tried the phone jacks inside the house, they were all working fine again. Somehow the opening and then closing of the NID door must have fixed the problem. Very strange. And as I said, this has happened to us twice so far over the last several years.
Interesting. We've been losing our dial tone on and off for past 2 months - seems like we lose it when a bad rain storm hits. I was about to replace our wall jacks 2 months ago when all of a sudden the dial tone came back after doing basically nothing (I had replaced the cord and thought that had fixed the issue, but it went out shortly thereafer). I was going to test a dial tone out of the NID, but it came back on its own so I never did that step. Dial tone is out again today 12/29/18. Reluctant to call for service as there is a steep service call fee you incur.