Please add your Gatsby Cloud Content Sync URL to the WPGatsby plugin settings page.
Please ensure your URL is correct and your Preview instance is up and running.
If you've set the correct URL, your Preview instance is currently running, and you're still having trouble, please refer to the docs for troubleshooting steps, ask your developer, or contact support if that doesn't solve your issue.
If you don't have a valid Gatsby Preview instance, you can set one up now on Gatsby Cloud.
Please visit the docs for instructions on setting up Gatsby Preview.