If your browser console shows BillingNotEnabledMapError or the message "You must enable Billing on the Google Cloud Project," Google Maps cannot load on your site.
Why this happens. Billing is not enabled on the Google Cloud project associated with your Maps API key. Google offers a generous free monthly tier, but it still requires billing to be set up.
What to do. You do not need to recreate the API key. Enable billing on the key’s project through the Google Cloud console.