i had the same problem. RUTX09, SIM from Deutsche Telekom, no internet... (latest firmware)
The SIM was connected - but with a IPv4 adress = 10.127.x.x ..... Didn't know where this ip came from, but 10.x.x.x are not routable within the internet.
Solution for me: Network -> WAN -> MOB1S1A1 -> Auto APN off
APN = Custom
Custom APN = internet.t-d1.de
.... now I get a 37.81.x.x adress and everything works fine..