I had something installed called Yoast SEO (think I wanted a particular type of XML sitemap some time in the distant past) that as a byproduct of whatever it was trying to do ended up redirecting the /author/myname path on workdpress to the root of the site, which meant I wasn't discoverable on activitypub even though the webfinger bit was working fine and I could see the hits to the webfinger URL on the apache logs.
I don't know if it would be possible somehow to make diagnosis of this easier, some way to say your webfinger is fine, but your author bio is borked.
Not really the fault of this excellent plugin in any way, but it cost me some time and some folk might not get to the bottom of it if they are in a similar situation with some conflicting plugin.