Hello, I have downloaded and installed the emscripten SDK and restarted the launcher and editor. I now see “Firefox” under the launch menu, and launching appears at first glance to work. However the page hosting my game never loads in Firefox. The error is rather simple at:
Firefox can’t establish a connection to the server at 127.0.0.1:8000.
Using 4.7.1
Hi,
When you launch on firefox, do you already have firefox windows open? There is an issue with launching on the firefox (and some other browsers) that cause the launch service to close too early. The workaround is to close all firefox windows before launching, which is a pain, I know, Sorry 
There are fixes for this in the main branch but they didn’t make 4.7
Thank you this did indeed resolve my problem!