Samsung screen does not lock.

[AC Question]

I have samsung GT 5500 android 2.2

The screen will not lock, it usually locks when screen timeout but does not any more.
It also usually locks when press end call button but does not.

I normally see the green padlock icon which I have to swipe to right to unlock.

It's happened before and I found a solution by pure chance, but unfortunately I cannot find it again.

I'm sure it had something to do with gmail but uncertain.

Please help.

 

[B. Diddy]

Welcome to Android Central! Have you checked your Settings>Security options? I'm not sure what it's called on Samsung devices--something like "Screen Security" or something like that. On my Nexus 5, it's Settings>Security>Automatically Lock​.