When trying to install a signed application (app-release.apk), a "Blocked by Play Protect" alert is shown and the app is not installed. However, an unsigned application (app-debug.apk) can be installed without problems.
The error message:
Play Protect doesn't recognise this app's developer. Apps from unknown developers can sometimes be unsafe.
Why this error happened? What's the solution?
I found the solution: Go to the link below and submit your application.
Play Protect Appeals Submission Form
After a few days, the problem will be fixed