Unable to claim threefold repetition

Is there a reason why I couldn't claim draw by threefold repetition after move 36?

http://de.lichess.org/ZzorJThM#71

I did offer a draw a few moves before.

in the preferences, did u click on the "always" button under Claim draw on threefold repetition automatically? because if u didnt that might be the problem but if u did i dont know what happened...

No, it's "when time <30". Normally, I would get a choice to claim draw or not, but it just didn't occur.

maybe its a bug...