Unfortunately, I'm not familiar with dealing with rpgmaker issues on Joiplay, it seems to be looking for a png file even though it should be a rpgmvp file, it might be related to extracting with Japanese name encoding, but I'm not sure how you'd do that on mobile. I'm not sure what extraction app you're using, but on winrar under the options tab, there should be a name encoding tab where you can select Japanese Shift name encoding, then extract. That's all I can really think of, sorry, I can't be of much help, but there might be someone else here who has played it on mobile that can help you.
Edit: Disregard what I just said, I just realized you said that it worked before patching it, so what I said about extracting doesn't really matter. But like I said, I'm unfamiliar with Joiplay and how the patch might be affecting the files there so I can't really be of much help.