A few people have had problems getting the D9200 with ArcadeVGA to work with the Act-Labs gun.
I finally have an explanation as to why most people have this working but a small minority have problems. The issue is this:
P1279201 Video/Sync input board for the D9200. The older Rev. B version did not work with the Act-Lab light gun but the newer Rev. D version is fine.
Wells-Gardner tech support are aware of this issue. The boards can be upgraded but there are many components to change. I expect W-G would be able to do some kind of swap-out, but I would not think, or expect, them to do it without charge, as it's not really a defect in the design but a compatibility issue.
Andy