Android M has new battery saving features that can cause Alarm Clock Xtreme to not function properly when sleeping which causes the alarm to not go of on time. We’ll create an app update shortly to solve these issues. The following guide might reduce the effects, but is not definitive. We advise users on Android M to use the Google Clock to wake up until these issues are fully resolved.
Step 1: Go to Android Settings and select “Battery”
Step 2: In the battery settings open the menu
Step 3: In the menu select “Battery optimisation”
Step 4: In Battery optimisation select “All apps” from the dropdown
Step 5: Select “Alarm Clock Xtreme” from the list
Step 6: Select “Don’t optimise” and “DONE”.
You alarms should now work as intended.