NR7103 - Flashing firmware

Hello,
I have NR7103 from mobile operator. I cannot login to the administration. I think that they have some special custom firmware because im also unable to factory reset the device. I tried to reset it, but both LEDs started fo flash quickly and afterwards im still not able to login into administration. I also tried supervisor account, but it is telling me that supervisor account is disabled. Also wifi is disabled on the router and i cannot start it. So there is question if it is possible to reflash somehow the firmware? This device has also USB C port but i did not find any application how to configure the router through USB C cable.

Thanks a lot for any tips.