From the troubleshoot file it seems that the device has mobile connectivity issues. Thus, it cannot connect to RMS. So let's try to troubleshoot the mobile connectivity issue first.
The device successfully connects to the operator and obtains an IP address. However, the device fails to access the internet. I have noticed that you have configured failover for mob1s2a1 interface, but not for mob1s1a1 interface which you are using with your SIM card.
Hence, could you please navigate to Network -> Failover, enable failover for the mob1s1a1 interface (not mob1s2a1 or others) and drag this mob1s1a1 interface to the top of the list, so that it has a metric of 1. Save & apply changes.
Give it a few minutes and then navigate to System -> Administration -> Troubleshoot. Under the diagnostics section, enter the IP address of 188.8.131.52 and press 'perform'.
If the device has internet connectivity, you should see successful pings in the output. If pings are successful, check if the device connects to RMS. If pings are successful, but the device still cannot connect to the RMS, try to reboot the router. In case the device has internet connectivity, but still cannot connect to RMS after the reboot, please, generate another troubleshoot file and attach it.