Firebase OTP working fine on debug apk but not release apk

I am using flutter and firebase OTP. The SMS is received while running the debug APK of my app. However, I am getting this message while running the release APK using the command flutter run --release.

This is the returned message:

This app is not authorized to use Firebase Authentication. Please verify that the correct package name and SHA-1 are configured in the Firebase Console. [ A safety_net_token was passed, but no matching SHA-256 was registered in the Firebase console. Please make sure that this application’s packageName/SHA256 pair is registered in the Firebase Console. ]

Kindly note that I am running this app directly on my phone and not by installing it from google play.

I tried the following on firebase console:

1. Debug keys
2. Release Keys
3. Google Play signing and upload keys certificates.
4. Also my google-services.json is up-to-date.
5. Flutter clean and pub get before running in order to make sure that the changes will occur.

I tried all the solutions presented by similar questions such as adding an email in firebase, adding google play keys, etc. and unfortunately none of them worked.

Update: Solved, the problem was wrong naming inside the manifest file as the error message stated:
Please make sure that this application’s "packageName/SHA256" pair is registered in the Firebase Console. Usually, it is the sha1 or sha256 keys, however this time it was the package name.

You have to generate SHA-1 for relase build and add it to the firebase console for the same project that you have registered.