indexing.canonical-invalidThe canonical link can't be trusted
Why it matters
A canonical link is only useful if search engines can act on it. Google ignores it when there is more than one and they disagree, and when it sits in <body> instead of <head>. A relative address works until the page is served from another host or a staging copy, when it silently points at the wrong site, so Google recommends absolute ones. A canonical on another domain hands that domain the credit for this page: right for syndicated copies, a disaster when it is a leftover from a template or a staging site.
Source: How to specify a canonical URL and its troubleshooting notes.
How to fix it
Keep exactly one canonical link, inside <head>, with a full https:// address:
<link rel="canonical" href="https://www.example.com/this-page" />Two usually means the theme and an SEO plugin both add one: switch one of them off. One in <body> usually means something earlier in <head> (a <div>, an <img>, a tracking snippet's <noscript>) isn't allowed there, which ends the head early: move that element out.