Skoda Octavia: No Radio Communication?

Hi, Skoda Octavia Estate (Wagon/Station Wagon) 1U, year 2003, ASV engine, 169,000 km.
The dashboard displays the following error message:
Address 17: Combination Instrument
Label file: RKS\1U0-920-xxx-17.lbl
Control unit part number: 1U0 920 841 J.
Component and/or version: KOMBI+TRAVEL DISPLAY VDO V09.
Encoding: 19112
Company number: WSC 31480

"One error found:"

01304 - Radio
49-00 - No communication.

Once upon a time, a different radio was installed, although it was also a Skoda radio. I can access the radio's settings via diagnostics, and there are no error codes stored. Is it possible that the radio is not being properly recognized by the instrument cluster (Ki)? How should I proceed? If nothing works, I can disable the communication. Does anyone know which cable needs to be disconnected from the radio connector for that purpose? Thanks in advance.