(der) Vorführeffekt
noun: (literally) the demonstration effect
The Vorführeffekt occurs when something stops working, only for it to start working again when you ask someone for help with it.
For instance: your computer stops working; you ask someone to fix it; it miraculously starts working the moment another person comes into play.Das ist halt der Vorführeffekt. = It never works when someone’s watching. Sobald ich um Hilfe bat, trat den Vorführeffekt ein. = Just when I asked for help, the demonstration effect set in.
Two women looking at a computer. Photo: Free-Photos via Pixabay