VW OBD Access: Car Not Accessible?

Hello,
"Does anyone else experience the problem where I can easily read error codes and scan control units, but apparently, VW's diagnostic tool can't even read the VIN? Three weeks ago, it worked fine at the same VW dealership. The only thing that happened in between was that a tuning shop made a backup of the engine control unit's settings, but they claim they didn't write anything new."
At the same time, I can access the system without any problems, and no errors are displayed. Also, a local repair shop was able to access the OBD interface using Bosch software on the same day.

According to a technician at VW, it could be due to a fault in a cable that is only used by the VW system for diagnostics.

Maybe someone has an idea what this could be?!

Thank you!