Have you tried installing an application and you observe that install button cant press but the cancel button works. Its obvious something is wrong and rebooting your android device for 20times won’t resolve the issue, so here is what to do.
Either you are using screen filtering apps just like Twilight, f.lux, CF.lumen and bluelight filter.Do this to get this done:
Try deactivating/uninstall/for-stopping the screen filtering app and it will you should be able to use the install option button as normal.
This works 90% most of times, but if this doesn’t work try looking for all installed apps that have overlay permission (apps that can show their contents over another apps) E.g (Messenger, Musixmatch, Touch Assistant apps that can float on your screen)etc.
Try disabling them one after the other in your Settings to identify which one is causing the problem.
Also search for “Draw over other apps” menu in your android setting where all the apps with this permission will be listed.
Congrats, you just resolved the install button not pressing!