AMP Page URL has canonical URL which is disallowed
This means that the URL in question is an AMP Page URL, and contains a canonical tag pointing to a disallowed URL.
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 is disallowed in robots.txt, then something has been configured incorrectly.
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 is disallowed then search engines cannot 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 is disallowed in robots.txt.
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 was disallowed by a robots.txt rule, for example:
How do you resolve this issue?
Assuming the canonical is pointing at the correct URL, you would need to update the robots.txt file and remove/amend any disallow rules that stop search engines from crawling it.
If the canonical is pointing to the incorrect URL, 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 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/