Silent failure during setup caused by blocked third-party cookies

After struggling with this setup for far too long, and after the usual experience of trying to get help from the Meta Help Center (which was, unsurprisingly, not very helpful), I finally found the actual issue.

The connection process fails if your browser blocks third-party cookies. The setup appears to work, shows that WooCommerce is connected to Facebook, and then the popup just goes black or gets stuck. There are no useful error messages, no clear indication of what went wrong, and the plugin logs only show that the access token is missing afterwards.

The solution was to temporarily allow third-party cookies in the browser, complete the Meta connection, and then disable them again.

A simple warning in the setup screen would have saved hours of troubleshooting. Expecting users to diagnose a silent OAuth failure caused by browser privacy settings is not exactly a great user experience.