How do I get a draw by repetition adjudicated?

My opponent keeps repeating moves and I'm entitled to a draw by repetition, but the chess.com program does not automatically award the draw. How can I get an adjudication?

If the current position has been repeated at least three times, simply click the "Offer Draw" button. If the position has truly been repeated, the game will immediately end.

CLAIM Draw (in turn-based). 

Thanks for the replies. "Claim Draw" showed up on my screen, so it's finally over...at Move 84.

The claim draw button did not appear, and a draw offer did not automatically enforce the rule in this game http://www.chess.com/echess/game.html?id=45144811

My move makes the third repetition of position with White to move:

r1b2rk1/5ppp/p2b4/1p1p4/3P1q2/2P1R2P/PP3PP1/RNBQ2K1 w

after my moves 15, 17, 19.

Perhaps there is a bug.

Clicking the Draw button should now end the game in a draw.

It did, but only because my opponent accepted the resulting draw offer.

The website should have awarded the draw automatically. As it is, my opponent could have made a move that does nor repeat any of the twice repeated possibilities, and then the time for a draw by repetition would have passed--an injustice given my effort to claim a draw.