With Huawei devices, to allow Zoiper to work on background you need to do the following:
- Install ZoiPer and start it.
- Select "No" when prompted to "ignore battery optimizations"
Open Android Settings - Apps - Advanced
Select "Ignore Battery optimizations"
Select filter "All apps".
Find Zoiper and set it to "Allowed"
And to allow Zoiper to work while your screen is locked you need to also do the following:
- Open Android Settings
- Search for "Applications"
- Find "Zoiper" and tap on it
- Select "Battery"
- Enable "Allow Execution when screen is off"