You mean the http redirect to https is up but the https site is down.
curl http://status.slack.com <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> <html><head> <title>302 Found</title> </head><body> <h1>Found</h1> <p>The document has moved <a href="https://status.slack.com">here</a>.</p> <hr> <address>Apache/2.4.7 (Ubuntu) Server at status.slack.com Port 80</address> </body></html>
The HTML parts are fallback for if your browser (or curl) in this case doesn't handle a 302