That is a signal problem, but whether it’s the SIM or the antenna (maybe a loose connection) or just plain poor signal will require some troubleshooting. If you can, I’d try one of the cameras that’s in another location at that location. If the working camera no longer works when it’s in that location, it’s the location that’s the problem. If that camera works, then swap SIMs and test both cameras, and if it’s not obviously the SIM, swap antennas.
You have the means to do some troubleshooting to identify the exact problem because you have both working and problem cameras.