Error: Call to undefined function Drupal\firebase_ui\Form\user_role_names() in Drupal\firebase_ui\Form\SendNotificationForm->buildForm() (line 110 of /var/www/html/modules/contrib/firebase_ui/src/Form/SendNotificationForm.php).

Thank you for reporting the issue.

This problem occurred because the user_role_names() function was incorrectly referenced. I have fixed it by using the correct method to load user roles within the SendNotificationForm class.

The fix has been committed, and the error should no longer occur when selecting Specific Roles in the Send To dropdown.

Please update the module to the latest version and let me know if you face any further issues. Thanks again for helping improve the module!