Google has added a security system for apps that are not downloaded from the Google Play called "Play Protect". It is possible that the Mobile Tracker Free application is detected as potentially dangerous.
To prevent the app from being uninstalled, you must disable Google Play Protect.
- Disable Google Play Protect
Open "Play Store" application => tap on Menu button => select "Play Protect" option => Disable the options "Scan device for security threats".
- Disable Google Play Protect Notification
1) On Android <= 7
Settings => Notifications => Google Play Store => Block all
2) On Android >= 8
Settings => Apps => Google Play Store => Notifications => High priority => Turn OFF