I had used the file manager app for previous attempts as well. I just recently tried installing the apk on two other androids I had lying around, and the same issue came up with both of them. I also tried downloading from separate devices and moving the apk over to my phone with no luck. Recently I looked into potential reasons for the issue and found that sometimes compression caused by downloading with Chrome can cause this issue, so I tried downloading with both duck duck go and Firefox, but that didn't work either. I've installed a lot of apks, but this is the first time I've seen this kind of issue.
Viewing post in Separate purchase?
If you'd be able to join the discord above and @ me I could have renpy export additional android builds that are more specific and send it over for you to try. It guarantees the universal version works on most devices but I can always set up an extra android build in case the universal one's failing and another works instead.