…which means, the keeper.exe is missing. I suspect it’s also located in the /data folder.
Now this is getting rather complex, because your directory structure seems to be different from mine.
1. Try this:
mount c: /storage/emulated/0/Dkeep1/data
imgmount d /storage/emulated/0/Dkeep1/data/game.gog -t iso -fs iso
2. or copy keeper.exe, dos4gw.exe, keeper.cfg, game.inst and game.gog to /DKeep1, and use this:
mount c: /storage/emulated/0/Dkeep1
imgmount d /storage/emulated/0/Dkeep1/game.gog -t iso -fs iso