kolelguy Well, glad you got it working. The hidden menu method fix I suggested may only apply if the account/SIM/device doesn't already have CDMA-less provisioning properly enabled. So indeed the rep could have fixed it as well.
Furthermore, for anyone else having signal and/or MMS/SMS issues on a Verizon MVNO, I just stumbled on something potentially useful. Not too long ago, I used to be able to choose between 3G and 3G/4G auto via the normal settings menu (however, forcing 4G/LTE only was never an option here). Anyway, this "System Select" menu option now seems to be missing for me, even after a factory reset. I'm guessing my account/SIM was automatically updated at some point not long ago for CDMA-less provisioning, either that or the phone finally recognized the change, after a recent factory reset, hence the now missing setting.
This may be a good way to check whether an account/SIM has CDMA-less provisioning working under a Verizon MVNO with this phone. So to walk through. Under "Settings > Wireless & networks > Cellular networks" if you see don't see "System Select" you probably have CDMA-less provisioning already. However, if you do see "System Select" you probably need to contact your provider and have them enable CDMA-less provisioning. If this fails, you can of course try the hidden menu method I previously suggested.
Regardless, personally, even with my account now seemly having CDMA-less provisioning. I'm going to leave it set to "LTE" in the hidden menu anyway, just to be safe.
Lastly, I'm guessing the hidden menu fix/workaround may also apply to other providers with defunct 2G/3G (GSM/UMTS/HSPA) networks as well, assuming the phone is still trying to connect to those defunct networks, instead of just LTE. Not sure if a similar GSM and/or UMTS-less type provisioning is available with "GSM" providers.
whynot Thanks for the tip, fixed.