AMP Page URL has canonical URL which is Redirect (3XX)
This means that the URL in question is an AMP Page URL, and contains a canonical tag which returned Redirect (3XX).
Why is this important?
AMP HTML documents are required to have a canonical to the non-AMP equivalent (or a self-reference, if no equivalent exists). If this canonical is pointing to a URL that redirects, search engines may consider this invalid.
The canonical tag is a mandatory element for AMP pages to be considered valid, and the canonical tag is supposed to point back at the original 'non-AMP' version of the page. If this page redirects, then search engines may not crawl it, which makes the AMP pages more difficult to discover, and sends conflicting and confusing signals to search engines - increasing the chances that the AMP page will not show up in search results.
What does the Hint check?
This Hint will trigger for any AMP Page URL which has a canonical tag pointing to a URL that returned Redirect (3XX) when Sitebulb attempted to crawl it.
Examples that trigger this Hint
Consider the AMP Page URL: https://example.com/amp/page-a/
The Hint would trigger for this URL if it included a canonical URL,
where this canonical URL had a 301 (Permanent Redirect) header response:
Similarly, URLs with other 'redirect' statuses will trigger the Hint (i.e. any other 3XX response).
How do you resolve this issue?
The canonical should be pointing to a URL with 200 status, not a redirect.
To rectify the issue, you would need to fix the canonical on the AMP page so that it points back to the (correct) non-AMP version of the page, and ensure that this page returns status 200.
You would also need to ensure that the non-AMP version of the page has a self-referencing canonical. It should look like this:
For the URL: https://example.com/pages/page-a/
This page defines a self-reference canonical and an AMP page:
Then the AMP page has a canonical pointing back at https://example.com/pages/page-a/