When creating content that includes an RSS feed, either Feeds or Tickers, Beam will validate whether the URL you have entered is a valid public RSS feed. If it is not, you will see this error.
If you are seeing this message and know your link is a valid RSS feed, it’s likely that the creator of the feed blocks automated data pipelines and scraper bots for security reasons. In that case, when Beam tries to validate the URL, the server returns a 403 forbidden or 403 misc error message, and we cannot validate the feed.
To work around this, you can run your URL through a free public RSS generator/cleaner such as Feedburner. This will fetch the data and serve it back out via a validator-friendly URL.