Place it at the exact point a plan visibly fails, after the setup and before the reaction shot. Follow it with the Windows XP Error for a tech failure, or with the Womp Womp Fail when the joke is a personal flop, letting the second sound close the scene.
Über diesen Sound
This is a brief spoken clip, just over a second long, built around the flat declaration 'It's not working.' The voice sounds strained and defeated, as if a plan has already collapsed before it can be explained. It lands as comic frustration, the kind of exasperated sigh that makes a small failure feel instantly recognisable.