Game Randomly Became a Draw

This game randomly became a draw even though a few turns before the end I decline a draw, and nothing in the interface told me why the game was a draw

It is a chess rule called three-fold repetition. The position repeated on moves 46, 48 and 50.

Threefold repetition. The position is identical at the end of White's 46th, 48th and 50th move.

Play 49...Kd2 and you win.