If the app is closed, nothing can be done from the app, also not " for a while".
There are many misconceptions about the term “background”. Background as used here means only that the app is not visible (eg after pressing the home button or after time-out / in sleep mode), but not closed. "Background tasks / services" means that an app can also execute somthing if the app is closed. That's is indeed not possible with AI2 & its clones (AB, Thunkable, Kodular, ...).
So show your blocks or post the aia.