Play store error #963 I have a Xiaomi redmi note 4, last week, I flash super su with TWRP, I change the sd mount to EXT4 because I have a problem, but is solved, and I wipe data. When I reboot the phone to system, all is OK, but I can't install any apk from play store, I get the error 903. I try to wipe data, wipe play store cache, uninstall the updates, reinstall play store, wipe data of google play services, etc... But nothing works. Right now im using Aptoide, please help, thanks you.
When using the methods reported by @Izzy, none of them solved the issue on my Galaxy On7, rooted to work with Android Pie (9), LineageOS 16 flavour -- using an SD Card as adopted storage.

Here is what I did:


After enabling Developer Options, I checked the option "Force Allow apps on external" 
Cleared the play store data;
Rebooted the device


Now all apps on playstore, which I had forcibly moved to the sd card with Titanium Backup, are able to be updated with no issues.

Hope this helps