I was trying to install third app apps (to be exact, custom kakaotalk themes) from an unknown developer, and everytime I tried to install one, I'd receive some kind of google play popup telling me the app is from an unkwown developer and might be unsafe. One time I accidentally tapped "ok" instead of "install anyway" and now it won't let me install that app - everytime I try to open the apk and install it, it shows a message saying "app not installed". Sorry if this is a dumb question... but is there any way to fix this? Yes I have unknown sources turned on (I can still install other themes anyways, except this one which I accidentally denied). I tried to clear all the data and cache from google drive (the app that i was using to install) and google play, rebooted my phone, etc, it still doesn't let me install it. My phone is a Xiaomi Redmi S2, MIUI 10.2 (android version 8.1.0).