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Edit file /api/conf.d/firebase.php - add 4 characters “<?php” to the beginning of the file and save it
4. Enable Firebase sign-in
Go to https://console.firebase.google.com/, then “Project” > “Authentication” > “Sign-in method” > “Sign-in providers”. Enable email/password provider.
Add your domain name to the "Authorized domains" in the Firebase console: “Project” > “Authentication” > “Sign-in method” > “Authorized domains”