I have this exact same problem in my MY 2011 Multivan T5.2. VCDS shows an error of "antenna not connected" for both antennas. This is how I bought the van used.
I suspect the problem is the connection to the FM antennas (which is actually located in side mirrors)
I will check the connections behind the radio and inside the door panels and report back.
More details on the antenna locations here:
MY11 T5 - I found the antennas
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