I'm reffering to this particular topic: viewtopic.php?t=129271
I experienced the same problem - when changing my location (so the modem uses another transmitter tower) it wouldn't connect.
After turning the router on at the original location, it connected immediately.
My device is a RBSXTR&R11e-4g LTE-Router.
I tried upgrading the LTE-Modem firmware using the tutorial in the reffered topic, where I've only been kind of successful. After some research, I noticed that there's a new "firmware-upgrade" command (/interface lte firmware-upgrade lte1 upgrade=yes). Before using the new command, I tried upgrading the firmware using AT commands but I always got an "operation not supported" error replied.
After I ran the firmware-upgrade command, I managed to upgrade the modem from firmware version v005 to v007. Unfortunately I at least will need version v008 to solve this problem.
Do you have any ideas how to solve this?