No XM signal.
 

I have a 2012 Silverado truck with factory Sirius/XM radio. I have a camper which blocks the shark fin roof antenna, so I want to put a magnetic aerial somewhere on the hood.
Saw on line that this was easy - get a FAKRA adapter, unplug the connector on the back of the radio and hook up to the new magnetic antenna.
Have tried this with two different antennas and two different adapters and keep getting the same result - get a signal for about 1 to 2 seconds then nothing - radio shows no XM signal. Connect back the factory antenna nd works perfectly!
Any suggestions?

Sirius XM NGVA3 magnetic antenna giving "NO XM Signal"
 

I have the same issue of getting the "No XM Signal" notice when plugging in a SiriusXM NVGA3 magnetic antenna with a FAKRA adapter into the factory Delphi 28261210 (GM P/N 20938347). When the factory shark fin antenna is again plugged in, signal is ok. Trying to use magnetic antenna due to truck camper overhang is blocking the shark fin antenna. Any responses to this issue?