Did you figure it out? (It appears Bb5 was played.)
I am unable to make a legal move

I had to make the move on my android phone. On my Surface RT with win 8.1 using IE 11.0.96 I had the problem. I had the same problem again on a different game also on the Surface.
So i guess I will stick with playing on my phone until your QA team can replicate the problem and get it addressed by development. I don't know if the same problem will occur on a full sized PC as I only use the phone and recently the Surface for chess.
In a tournament game I'm trying to make a move, but the system will not allow it. I'm not in check, I'm not placing myself in check. The game is JayG67 vs Goirish3, f1b5. There must be a reason, but I can't see it.
Thanks.