Why does this keep happening?

@Col_Needham​ It happens in both Edge and Chrome and yes, I have flushed the cache. 

When I use the browser's Developer Tools and look at the console response, I see a 503 error. 
"Failed to load resource: the server responded with a status of 503 ()"

@theDaviator​ … and in a private browsing / incognito window with all plugins and disabled?  If you have any VPN software installed, try disabling that, and if you have an alternate network connection (for example, WiFi via your phone) does that work? 

Turning off extensions seemed to do the trick. Thanks. 

@theDaviator​ Good to hear -- please can you report the bug to the author of whichever extension caused the problem.