In the Associated Platform tab for the emulator did you add the platform name?
>Tools>Manage Emulators and edit your Mame. Check the Associated Platforms tab.
Sharing pics of your edit emulator screen would help. (Pic of the main details tab and the Associated Platforms tab).
Not sure why you have 3 Mame emulators, but since you do, you need to make sure the platform is listed in all of them in the Associated Platforms tab.