RM505Q-AE 'no service' on zebra tablets

Dear,

We are having issues with several Zebra tablets that have a RM505Q-AE module integrated.
Windows indicates ‘no service’ The apn is correct and devices are fully up to date.
is there anthing we can do firmware related? or in trying to find logs on what exactly goes wrong?
any help would be appreciated

when tying to connect to the module with AT command tester , the connection fails ‘invalid or no response from the device’