PSA
Looks like GitHub is currently having a major outage. This outage will prevent any plugin from installing via CA (including CA itself for new users).
CA itself is still operational (although it takes a bit longer to start up), as it is automatically switching to the backup server, so docker installations will still work. However, some icons may not appear (as they were hosted on GitHub), and if you're accessing your server via https, then the "lock" may break as since the primary appfeed server is down, all of the https cached icons are unavailable which means that whatever URL the template authors have dictated is where the icons will be grabbed from.
Once GitHub resolves their issues, CA will automatically revert back to the primary appfeed server on the next change of the feed (usually every other hour)