Two canonicals that disagree

The head names one canonical URL. The HTTP header names another. Both lose.

Mixed signals

You can set a canonical URL in the HTML head with a link tag, or in the HTTP response with a Link header. Search engines read both. When the two disagree, as they do here, the search engine cannot trust either one, so it drops them and picks a canonical on its own, which is rarely the one you wanted.

Pick one place

Set the canonical in one place and keep it consistent. Most sites use the HTML head tag and never touch the header. If a CDN or framework is adding a Link-header canonical you did not ask for, that is usually the cause. Line it up with the head tag, or remove it, so there is one clear answer.