I'm using Android 13, and it works fine for me. Please go through the instructions in Joiplay thread very carefully. If still doesn't work, ask the Devs in their discord.
I don't understand why you're downloading from Play Store. In the thread I was linking you to, they instruct you to download from Patreon. You don't need to pay for anything. The public version is available for all to download on Patreon. Download from there.
you have to play Part 1 to the very end and let the game export your progress.
provide a meaningful name to keep different playthroughs apart.
you start Part 2 by importing one of your exported game states. save files made by anything other than Part 2 are marked incompatible cuz there is simply no content of Part 1 to get Part 1 save files working.
keep in mind, only exported game states of my android port of Part 1 are usable!
from now on my android ports of Ren'Py games have a 2nd, persistent save location like windows. if you uninstall an app, the save files and persistent data remain intact.
therefore the app needs the permission to access the public external storage (or a new one on Android 11 ), because it has to read and write outside its own external storage directories.
you have to grant the permission or the app is shut down.
have fun and please report problems (you can reach me