Where have all the players and challenges gone???

From last few days I have been observing that no. of games and challenges are declining day by day. Right now I did not find a single game open to play. No player is shown in the main window. I created a game and have been waiting for response but no player to play.

You're currently marked as a computer assisted player, which would be your problem.

computer assisted? how and what does this mean? how to unmark ?

Means that you've triggered the anti-cheat system.

I'm not sure how you appeal, but there's probably an answer in the FAQs