I have gone from having one or two users experience this on occasions to most users regularly, and now today all users every time.
Trying to load with console open on chrome to see what happens it shows 404 errors from shinyapps.io but shinyapps status page shows no issues.
Till now I was unable to diagnose the error as I was always able to get in and because I now know that users are getting a 404 they never connect to the app to generate a log file which explains that.
This is happening across multiple apps on the shinyapps servers.