RUT X50 Losing Mobile Connnection

Hi there. I have a RUT X50 where I have my main internet as WAN (wired) and then backup being a 5G SIM Card with external antenna. The antenna is fine and gives really good signal value - however, on the failover side the mobile connection keeps going to “offline” - a few times it switches to “standby” and then goes back to “offline” - any idea or help on what to do ?

Both Firmware and Modem are updated to latest versions ?

Right now I am struggling a bit as the main reason for the RUT X50 was the failover

OK - forget it - turns out i was out of data on my internet (backup line) - no issue as soon as I made sure I had enough data with my subscription