Sasmung s4 back button

So how did you install TWRP and what else did you do (e.g. using it)?

And are you sure this TWRP was for precisely your phone model?

 

Ive got the same problem too.

 

Same model, started after installing TWRP? Any more info you can give would be helpful.

 

He's right sounds like you used an s4 ROM For twrp wasn't the right model type SG4 so for now you might want to install button Savior apk from the Google Play Store then search into it look for more compatible ROM and make sure you got the right one for your model type SG4 phone and count your blessings that it was just a button malfunction it could have been much worse outcome,good luck.