Since yesterday, I see trouble loading some websites. It turned that many of my bookmarks were for HTTP versions of sites. Once I fixed them to HTTPS, they worked. I even saw trouble downloading files with software like download manager. HTTP would not work, but HTTPS would. All that worked 3 days ago. What has changed? It does not look like browser(s) only.
Do you mean that you tried the same thing with multiple browsers, and found the identical behavior?
Sometimes the most obvious explanation is the real one: the sites moved to https, but didn't properly code for redirects from http requests. Or, worst possibility of all, when they started listening on 443 they stopped listening on, er, whatever the heck port number is used by default.
Are there sites that redirected fine last week, and no longer do so?