RUT950 Lost serial number and MAC ID after fw upgrade

Dear all,
I performed a FW upgrade to a RUT950 from legacy firmware 6.09.5 but became unresponsive.
With bootloader recovery option I was able to flash again 6.09.5 and restore operation.
However it looks like it lost serial number, MAC ID etc… therefore it won’t connect to RMS.
I understand older devices (RUT950 G1**) are not supported by latest firmwares, however I cannot tell whether this is a legacy device or not. Its name on the invoice is is RUT950U022C0

This case is similar to https://community.teltonika.lt/t/rut950-rms-issues-strange-mac-address/5118

Can you help me?

With regards
Nick