This happened to me too. I cannot figure out the problems.
board too small
I use a laptop (netbook) with a very small screen with a nice big external screen. When I unplugged my external screen, played a couple of games and plugged it back in again, chess.com seems to think I still have the little screen plugged in - and even if I magnify the web page, I get aq fuzzy chess board - ie small but blown up rather than big. I will try clearing my chrome history and unplugging and plugging in screen again.
I went into settings on the live page and set the board to "huge" (!) and now it seems fine! Hope this helps you.
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In a recent update to the live chess application, the board size is stuck on "extra small" or something. No matter what I set my board to in settings, even extra-large, the board is still too small to see. This makes it very hard to play =( I'm using Firefox by the way. Just FYI.