A
I solved this as follows:
1. Tap "Setting" > "Sound and notifications">"Interruptions">"When calls and notification arrive". Then select "Only allow priority interruptions".
2. Now come back to "interruptions" and under "priority interruptions' select "Events and reminders" . Remove tick from rest of all.
3. Come back to "Sound and notifications", Scroll down and tap "Application notifications". Scroll down to find "Clock" and tap it. Set "Priority" and "Sensitive" 'ON'.
I hope this works.