Cruise Control Problems AFN

Hello,

After reading the existing posts, connecting everything, and having the friendly mechanic at the workshop try to unlock the GRA (Gas Return Actuator) in the control unit yesterday, the GRA still doesn't work.
When attempting to unlock it, the control unit behaves as if it's not accepting the code. Could it be that it's already unlocked at that point?
If this is the case, the control unit will not receive any signals from the switch. However, according to the cable measurements, the connection appears to be correct.
Are there any engine control units (ECUs) for the VW AFN engine that are not compatible with the cruise control system?
What is the unlock code? Perhaps the person at the workshop was mistaken.
I must also mention that the engine is installed in a VW Bus T3.

Best regards and thank you, Achim.