Two days back I had to do a factory reset on my android (v2.3.6). After that, I noticed that my phone display won't turn off after 30 secs idle time, even though the settings has been done appropriately. After 30 secs, the brightness decreases, but the screen won't turn off. Is there any other setting which needs to be changed here?
You can try the wakelock detector app which will tell you the application which is restricting the phone from going to sleep and lock mode.
Unfortunately it did not work for me since my kitkat version required the ROOT permission.
I fixed it by going to "Settings > Apps > Running tab". I closed all suspicious application in "Cached" and "running' mode.
It was one of my recent ip-camera phone app or the Alexa app which was restricting the phone going to auto sleep after 15 seconds and then to lock state.
The phone is working fine now after closing those 2 apps, I can run them when required.
Hope it helps.