That sounds very frustrating.
Did your son check to make sure the cameras were actually taking pics and just not sending them by looking at pics on the SD cards? That is certainly more likely than the cameras not taking pics at all, but it pays to check.
Did your son take/send a manual photo? I do that with all my cameras to be sure that they are back up and working?
I'd recommend that he set the cameras to default, take/send a manual picture or two, then reset to the settings you have been using by requesting a settings update from the app (if you are using premium).
You mention auto renewal, so are you using the $14.99/month plan or one that's similar? I've never used those, I've always used the plans that don't auto renew:
$25/2 GB/90 days
$45/2 GB/180 days
$75/4 GB/1 year
I've seldom let one lapse but when I have, once I paid, the camera started working very soon after I paid.