Hmm, ok, well I only have Gradius V PS2 ROM available for testing (I dumped it from disc myself as it was the only PS2 game I own which is on CD and the RA disc dump function doesn’t seem to yet be able to rip PS2 dvd game discs, not for me, at least); I can’t see Gradius V in that list, however there is a video on the Play! blogpost in my first post which seems to show this game running on the core?
Also, not convinced the problem is down to the game being loaded itself, as I can’t even get that far; any other core I try to load under Load Core option immediately shows in the bottom left of the RA menu, without the need to even go near any game content. Play! is the only core to just back out to main menu and return ‘No Core’.
Incidentally, I just sent the Play! dll to the same friend I mentioned in my 2nd post who previously sent me the MAME 2016 core dll; he’s just tested my Play! dll and see the same behaviour, the core shows up in the list of cores but it will not load.