I've got a VHF radio with an AIS receiver built-in. I've also got a Vesper Marine AIS transponder but I never see my own AIS transmissions on the VHF radio. As a result, I'm not sure if my AIS transponder is working.
If your VHF radio has been programmed with the same MMSI as your AIS transponder (and it should be), then your VHF radio won't show your own vessel on it's AIS display. This has been confirmed with a Standard Horizon GX2100.
The same is true if you have two Vesper Marine AIS transponders (not very many people do, but we do :-) If both transponders have the same MMSI, then neither will "see" the other.