Factory towbar electric problem

Hi guys, I have factory fitted Westfalia detachable towbar. There is some problem with electricity and I spent many hours to examine what it is and still no answer. When connect a trailer no light. I don't see system message that trailer is connected. When I connect trailer tester , the lights are flickering. There is no 12v at pin 9. VCDS see trailer 69 and no faults. I checked all fuses in main fuse box next to driver seat and all good. I removed the trim on the left side of the trunk and checked trailer module and nothing strange. The ground is well connected. There are no other fuses visible around trailer module . Does anyone had similar problem?