How can I troubleshoot a 403 error when accessing Google Search using a custom search engine?

For custom Google Search engines, a 403 error often indicates an issue with the engine's configuration or access permissions. Double-check the search engine's settings to ensure it's properly configured and that the API keys or credentials used are valid. Verify that the search engine is not restricted to specific IP addresses or networks. Also, ensure that the query you're using doesn't violate any search engine policies.