Why is my j5 does not go to sleep mode.

Hello everyone pls i will appreciate it if anyone can help. I have a Samsung J5, the screen does not go to sleep, even if i press the power button, it goes off and comes back on, i don't know what the problem maybe, i have tried in resetting the phone, still it's happening, pls help me in this.

Try Safe Mode. If no go, you could try flood cleaning the Power button with an alcohol-soaked swab. If still no go, repair.

Welcome to Android Central! Does the phone have the Smart Stay feature?