Why cant i choose a best answer?

Every time i go to choose a best answer and respond it never saves or picks it even after i hit submit. Is it because im using a mobile phone and not a computer? (I live in the land of phone line only internet.) So mobile phone is all i have to browse and use the internet. I spent thirty minutes typing a response to everyone who answered my question as i was picking the best one and when i hit submit it took me back to my question eith no best chosen. Is there a setting on my phone i need to activate in order to get it to do this? Please help because i just waisted thirty minutes for nothing.