The URL in question is an AMP Page URL, which contains a canonical tag that points to a URL already canonicalized elsewhere.
Why is this important?
For a valid AMP HTML document, correctly configuring the canonical link to the non-AMP version—or to itself if no non-AMP version exists—is essential. If the canonical points to a URL that is further canonicalized, it implies a misconfiguration.
The canonical link for AMP pages serves as a signal of original content. If the AMP URL redirects to yet another canonicalized page, it can confuse search engines, negatively impacting the AMP page's search visibility.
What does the Optimization check?
This Optimization is activated when an AMP page references an internal URL whose canonical tag points to another canonical URL.
Examples that trigger this Optimization
For instance, the AMP Page URL: https://example.com/amp-version/
The Optimization is set off if the AMP page’s canonical link is:
<!doctype html><html amp><head> <meta charset="utf-8"> <title>Example AMP document</title> <link rel="canonical" href="https://example.com/intermediate-page/" /> ...</head>...</html>
...and this canonical URL is further canonicalized:
<link rel="canonical" href="https://example.com/final-page/" />
How do you resolve this issue?
Rectify the canonical on the AMP page to assure it points to its non-AMP counterpart, which must possess a self-referential canonical:
For the original non-AMP URL: https://example.com/original-page/
The page specifies both a self-referencing canonical and its AMP alternative:
<link rel="amphtml" href="https://example.com/original-page/amp/"><link rel="canonical" href="https://example.com/original-page/" />
Concomitantly, the AMP version points back to the original non-AMP URL:
<link rel="canonical" href="https://example.com/original-page/" />