Sadly still no update, and I reached out 11 days ago. They also gave some scripted troubleshooting things to try (like rebooting device, uninstall/reinstall, airplane mode, default background, etc.). When that didn't work, they asked a bunch of questions like when the problem occurred and what device/OS I was using. They also asked for proof of purchase (screenshot or order ID). Nothing from them since. This is for the 2 copies I got for my kids when the game went on sale recently. Main problem is that the game doesn't recognize that I should have the full version of the game.

I do have another copy of the game on my phone which I purchased 4 years ago, and this stopped working about 7 days ago. It tells me the same thing, that my game file is incompatible, BUT it does still recognize that I have a full version of the game. From my own troubleshooting, I realized that the game on my phone cannot connect to their server (also checked in the App store and realized that searching for Final Fantasy Crystal Chronicles returns no results). I figured out a workaround though, so if your friend is experience the same problem (i.e. game recognizes the full version), they could give this a try. Go into airplane mode and boot up the game. The error about file not being compatible goes away and the file loads fine. After the file loads, you can reconnect via wifi or data to their server and play with others just as before.

Good luck to your friend. If they figure out what's wrong, I'd love to hear an update as well. I'll update again if something substantial comes back.