I’m getting the following error which causes a plugin (Cornerstone) to not function.
XMLHttpRequest cannot load https://metcast.co.uk/about/. Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://metcast.co.uk' is therefore not allowed access. The response had HTTP status code 503.
The error that cornerstone is throwing is:
A conflict on the front end of your site has prevented the preview from loading.
Would be grateful if anyone can help out