According to [#116466] uses client certificates available in Firefox. Security freaks can have their Firefox profile in a different more secure location, like for instance a secure encrypted container or partition. Client certificates are then not in their default location and LO will not be able to access links to client certificate secured content. Please provide (at least an expert) configuration for custom profile location or custom browser path.
it makes sense. Moving to NEW...
At least since LibreOffice-7.4 there's a button that looks like it does the job. (I haven't tested it) Options -> LibreOffice -> Security -> Certificate Path / Certificate -> Select NSS path @rs@comunica2.net Can you test if this fixes your problem? If yes, please close this bug.