Phone [Q] APK Crashes "Unfortunately "APPNAME" has stopped"

Hi everyone,

I have a Samsung Galaxy S4 (GT I9505) running Android 4.3.

I recently wanted to install an .apk file onto my phone and looked up the several methods. I have tried many methods but all of them lead to the same problem.

The .apk installs ok and launches fine but about 2 seconds after launching, crashes and says "unfortunately (app name) has stopped working". This is happening for any .apk file and with all the methods.

Is there something basic that I'm missing out here (eg. settings on my s4 etc...)???

Thanks so much for your help.