Newer Android version are sometimes very stingy when it comes to accessing system folders like Android/data. There is a chance that this won't work at all on your device, but you can try some of the suggestions here, maybe you'll get lucky.
If nothing works, you'll have to start the game over again. RenPy's skip feature is pretty neat, use it if you need to.
There's also the option of rooting your device but I'd only recommend that for more experienced users with extra time on their hands.
Just because you can't access the Android/game directory doesn't mean you can't install the game at all. Just skip that step. You may lose your saves, sorry about that, but the new Android version will store the saves on your shared device storage, so this won't be a problem anymore after you made the transition.
I understand that the new installation process is more complicated and that you'd rather have just a single apk to install. However, the maximum size of an apk file is limited to 2 GB. For comparison, the PC version is already 7.5 GB large! There's some magic you can do with media compression, but everything will look & sound worse and worse the more you're trying to cram into that 2 GB box. The transition to this new installation processes had to happen sooner or later, similar games of this size do it too. I hope you understand.
