Yeah, the FEN strings are the same for all 3 positions. And you know where to look for the draw option, right? There's no new button that appears, the normal "offer draw" simply changes to "claim draw". There have been complaints before about how that can be easy to miss, and it's only available for that moment in the game until the position changes again, but if you already knew to look for it there, I don't know why the offer didn't come up for you for that one turn.
The reason you can't claim it now is because the opportunity has passed-- that position would have to be reached again, or a different position for a third time.
Why can't I claim a three fold repetition in my current online chess game? The position with the same player to move was repeated 3 times.
It is my current game with Capa01. The positions with black to move on moves 47, 59, and 61 are the same and I never had the option to claim the draw