Alarm did not go off

Complicated to set up in the first place, I still had high hopes for this app but I tried it twice and both times the alarm didnt go off.. Yes I activated Night Mode, kept the app running and locked my phone. Both times the alarm didnt go off until I unlocked my phone and then the app told me I overslept. I dont trust it!

NBCHowington about Kiwake: smart alarm clock