We have deployed 15 of MX67C-NA with intent to use the integrated LTE modem for LTE failover. We have 15 SIM cards from Bell Canada that are all the same type of service. 14 SIM cards have all been installed and so far, 9 are working (under Cellular on the Uplink page, it shows Integrated Ready, fails over if WAN connection is unplugged) and 5 will not connect.
For the 5 that won't connect, it shows that it's attempting to connect and sometime briefly shows signal strength but then just disappears and never shows "Ready". Signal strength is sufficient in those areas, the APN is set the same for all sites and all of the SIM cards work in my phone.
I've tried re-seating SIM cards, power cycling (unplug power, wait 5 minutes, plug back in), tried different APN, tried removing APN altogether, but nothing seems to help.
Anything else that I could try that I haven't tried yet? I have a support ticket open with both Meraki and Bell, and both sides are pointing fingers at the other.