Troubleshoot communications Raven C3211

We have two sites that use Raven CDMA Model 3211 modems to download data from dataloggers. We have not been able to dial up the modem for over two weeks. Calling the numbers results in a busy signal. We tried powercycling the modems, when the problem first occurred. (That process worked in the past, but no luck this time.) The communications problems happened at the two separate sites at approximately the same time (last data received at 7 AM at one site and 8AM at the other), so we thought it was an issue with the cellular service provider. We verified that we there is an active account with our provider for the two lines. Verizon resynced the phones to the network and had us powercycle the devices again, and like last time, it was unsuccessful–lines are still busy when called. Does anyone have any ideas about what we could try next to resolve this problem? Thanks.

It seems C3211 is in end of life which is no longer supported by Sierra Wireless. Can you try and re-activate the modem using the Verizon Setup wizard: