To turn on/off your game notifications please follow the below simple steps;  

1. Go to your game settings  
2. Tap on notifications 
3. Tap on enable notifications so that it it's marked with a green "tic" and says "ON". 

Turn on notifications to be reminded of ingame events when they occur when you are currently not playing. 
To get notifications, you need to enable them in the device Notification Center, via Settings / Notification Center / My Hospital.