A6 4B: Navigation, Immobilizer, CAN Bus Issues

Hello, since no one has ever responded to my questions and concerns before,
I'll try it this way now...

Audi A6 4B, 11/2001, AYM.

I'm having the following problem:
When I unlock the car, either remotely or manually, and then open the door,
My car's AI (presumably the infotainment system) isn't starting. The engine only cranks for one second, the mileage, clock, etc. don't light up, the radio doesn't work, and I can't access the message system.
If I unplug the green connector from the AI unit and plug it back in, the AI starts immediately and all functions are available. This also works if I disconnect the battery for 5 seconds.
The error message in the diagnostic tool indicates a problem with the immobilizer and a communication fault between the bus system and the instrument cluster.
This usually happens when the car has been parked overnight.
VAG believes that the bus is not 'waking up.'

What now?

VAG would replace the entire AI system.

Thank you.

Frank.

And if you briefly turn the ignition on and off, does everything immediately go dark again, or does the instrument cluster remain on?

What also interests me is whether the interior light and the display in the FIS (multifunction display) work correctly for the driver's door. Normally, the instrument cluster (KI) receives a signal from the driver's door on pin 21 of the blue connector.

After disconnecting the green connector, the message appears in the memory, which is understandable because the connector contains both the W-line and the CAN lines .

It would be interesting to see if there is any communication within the measurement data blocks after the ignition is turned on normally, both in the instrument cluster (IC) and the engine control unit (ECU) .

The values of the measurement data blocks 20-25 in the combined data set, both before and after a potentially unsuccessful start, would be interesting.

Did you definitely check the fuses?

Have you also checked if all the power lines are connected to the combination unit?
All blue connectors: PIN 1 = Terminal 15; PIN 23 = Terminal 30; PIN 30 = Switch contact.
Check them all one by one, individually.