Battery managers allow mobile devices to extend their batteries but many times at the expense of performance, notifications and even shutting down background services. Boomerang in Child Mode requires to run as a background service and it's been found that Nokia's battery optimizer has gotten very aggressive with newer Android versions. Approximately, every 20 minutes if the screen is off, background services are killed.
Seems to be primarily a problem on Nokia devices on Android O (Oreo/version 8.0) and P (Pie/version 9.0).
Nokia's solution here isn't great but please try the following steps if you are finding Boomerang is not blocking apps or reporting app usage data
On your child's device:
- Go to Phone settings > Apps > See all apps.
- Tap on the right top corner menu > Show system.
- Find Battery protection app in the list, select it and Force close. It will remain stopped until the next restart. From now on, background apps should work normally and use the standard Android battery optimizations.
Additional information from a forum on Nokia's website: https://community.phones.nokia.com/discussion/3428/background-service-killed-even-when-whitelisted
Tips from https://dontkillmyapp.com/nokia