Entertainment unit error: "No suitable update found please insert valid update!"

Entertainment unit error: "No suitable update found please insert valid update!"

This is a problem out local VW garage has not managed to solve.

Regardless of ignition on or off, the entertainment screen shows this error message ever couple of minutes:

- Tried all the possible combinations of map updates on the SD card but the system doesn't seem to even register it being inserted. Also tried different format options and doing it from a mac and windows.
- I have taken the fuse out to try and 'reset' it.

I think the radio unit model number is 3Q0035874

Last resort will be to replace the main unit but it's not cheap.

Any reccomendations or troubleshooting ideas?

It's a VW Polo TSi 2015

Many thanks