Kaspersky app has the following known issues and possible solutions on ZTE devices:
The app may not start automatically after the device is restarted or the app is unloaded from device memory. In this case, you should start the app manually.
The app may be unloaded from device memory by the operating system. To fix this, lock the app in memory.
Some steps may be different, depending on the device model and version of the operating system.
Open Task Manager. For example, hold the middle button until a list of all running apps appears.
Find the Kaspersky app.
Tap the icon next to the app name.
The icon indicates that the app is locked in memory.
The app might stop working in background mode even if it is locked in memory. To fix this, change the application control settings in the battery settings.