I can't play on external servers on cellular data even though I have turned it on in settings. How to fix it?

I am not able to play on external servers on cellular data even though I have turned that settings on in the settings. It says you need to be connected to WiFi. 

Earlier it was ok, but then I faced a issue where I couldn't find the servers and to fix it I saw some articles and fixed it and I can play on WiFi. 

But I am a cellular data user so I can only play on data, and the game wouldn't allow me.
Please help.
I play MCPE on android.