Is it the case that id.loc.gov does not support HTTPS, or are they having a problem with it today? A simple Google search isn't turning up an answer.
In VIAF, we provide links from our records to the original source records. We provide those links using the same protocol that the user used to get to us. Apparently HTTPS links are failing today. (Maybe they've always failed and this is the first time it's been reported to us?)