To resolve it you can use Postman, if Postman does not return the XML error once you try a GET. You can perform some additional research after noticing that the site returned in a Postman GET to www.pbi-static.org, and I came across this link: https://cloud.google.com/storage/docs/configuring-cors#gsutil
Following the instructions to create a JSON file that allowed the Get verb and using the gsutil command given the issue can be fixed.
Also when creating a new static website, you'll get an error unless you follow the instructions in https://cloud.google.com/storage/docs/gsutil/commands/web.
An additional possible solution is to view the RSS Feed in CRM using Internet Explorer. The error notice will no longer appear. Chrome doesn't have a RSS reader built-in.