I downloaded and tried it on a Ayn Odin 2 and a Retroid Pocket 3+ on Joiplay v1.20.410 and RPGM plugin v1.20.53 and it works with no problems.
Unfortunately Joiplay is still in development and its behavior may change depending on the device.
The only suggestions I can give is to check the version of Joiplay and RPGM plugin and try dowloading again the JGP, maybe the last dowload corrupted the file
I do not play rpg games anymore, i only download it to unlock the gallery room, im tired of playing rpg games and wondering around forever looking for shit. all i want is THE ACTION!!!
but if its a rpg game by my favorite developer then maybe i will play it - like for instance monotool made a rpg game, i play it despite it being in japanese, waiting for english translation from dlsite, so i can make a thread for it here.