one trope I am SO INTO in romantic ships is Person A confesses feelings or hits on Person B and they are turned down. and then Person A moves on, but once they've put it behind them ... DOT DOT DOT now Person B is interested.
I don't mean fake 'doesn't remember the kiss'/'didn't recognize an obvious confession' nonsense bullshit, I mean they really were rejected: maybe Person B was having a terrible week, maybe Person B had personal problems & didn't have a thought to romance, maybe Person B was committed to someone else, maybe Person B has a negative impression that needs to be corrected...