This is a bit of a long shot, but it doesn't take long, so a try ain't that bad even if it wouldn't work- I assume you have a PC, not a Mac, so try to zoom like this: Place the cursor at any WHITE space of the app page at FB and CLICK. After that zoom by using key combination <CTRL> and the plus sign or the minus sign. Try…
I have the exact same problem - it was fine yesterday but today when I open the game I can see a much enlarged version and nothing on the right hand side...