Do you still have problems if you try it this way
Go into your facebook account, then into your chess app page from there. At the bottom on the left it says
"Merge Facebook/Chess Accounts
Merge your two accounts into one..."
Use that, but please make sure if you're entering an email address that it IS the one attached the the chess.com account you want to merge with
http://www.chess.com/fb-merge.html
i am unable to merge my fb acc and my chess.com. I have try many times and always come to a page like this..............
Our servers made a dubious move... and now you have to see this boring page. Sorry!
We're working hard to get this issue fixed - it should be just a minute or two. Please check back soon and we appreciate your patience!
I try many times