For correct work of application:
1) In “Settings ⟶ Device care ⟶ Battery ⟶ Power mode” select “Optimized” or “High performance”.
2) In “Settings ⟶ Device care ⟶ Battery ⟶ ⋮ ⟶ Settings ⟶ Sleeping apps” make sure that Prof Reminder is NOT added into the list.
3) In “Settings ⟶ Apps ⟶ Prof Reminder ⟶ Battery ⟶ Optimise battery usage ⟶ Apps not optimized ⟶ All” turn OFF Prof Reminder.