play protect does not recognize this app's developer

Question

I try to publish my app in a market that is not google play. When I try to install my app it says:

Play Protect doesn't recognise this app's developer. Apps from unknown developers can sometimes be unsafe.

I think the problem may be from the sign of app. I get release with another app but the problem stays.
What is the problem? Is it because of I did not publish in google play? Or maybe from the sign? Or maybe in there somewhere in my code?

Answer 1

The Google app bundle format uses your certificate from the app as an upload certificate. Google generates a new certificate after upload that is used for app signing. So since your app is not uploaded and published, there is no signing key, and app is blocked by play protect when you try to install it locally.

Answer 2

I released 1.0 version earlier. Now released 1.1 version.

1.0 before uploading on to Play console, I was able to install signed release apk, no issues.
1.1 before uploading on to Play console, I was - not - able to install signed release apk, and failed.

Looks like, play protect gives this error for an already released version on play store, if so, so this message should be seen as normal.

Once the 1.1 is pushed to play store, I saw no issues, so this error was just a false negative and can be ignored if you are updating the app.