Firebase phone authentication is not working after upload app on playstore

Did you just enrolled for Google Play App Signing? In that case your key has changed. You can get SHA1 of the key used to sign your apk from Play Store Console.

Using these steps you have successfully resolved all issues -:

1. Go to google play console
2. Setup -> App Integrity
3. copy SHA-1 certificate fingerprint in (App signing certificate)
4. Open Firebase console -> Project settings -> Add fingerprint
5. Paste your SHA-1 key
6. Now Reinstall your app from play

@HandyPawan's mentioned answer completely right here but as Google Console updated now the steps are -

1. Go to google play console
2. Release -> Setup -> App Integrity
3. copy SHA-1 certificate fingerprint in (App signing certificate) but no include (SHA1: )
4. Open Firebase console -> Project settings -> Add fingerprint
5. Paste your SHA-1 key
6. Now Reinstall your app from play