I have a profile that detects when certain apps are launched. I found that if you launch the app from the app icon or launcher, it works fine (even if the app is currently in the recents list). If you re-open the app from the recents list, it doesn't detect the app as running or sometimes detects it but takes a long time and possibly only when you pull down the notifications.
Android version: 9
Tasker version: 5.2.bf1