Put the associations of HTM and HTML back to IE for a moment. You can change them to your browser later.
https://www.winhelponline.com/blog/file-association-fixes-windows-10/ has the defaults in their HTM/HTLM and URL fixes.
This issue is not Black&White - therefore hard to explain (especially for Dummy). Essentially, links are not linking - both URL and local e.g. click on Win Orb to open C-Drive and get "...file does not have a program associated with it ..."
A URL link from elsewhere (doc/email) - other links will give "application not found". In most cases there's a work-around and in some instances the link works-e.g. from within websites. I or a malicious gremlin has caused this - how do I fix it? thanks