Pressing either new game or trying to load a game gives the following error:
An exception has occured, but exception handling has been disabled in this build. If you are the developer of this content, enable exceptions in your project's WebGL player settings to be able to catch the exception or see the stack trace.
in waterfox 56.2.9
21:15:39.938 uncaught exception: undefined - Exception catching is disabled, this exception cannot be caught. Compile with -s DISABLE_EXCEPTION_CATCHING=0 or DISABLE_EXCEPTION_CATCHING=2 to catch. (unknown)
21:15:54.086 Error: WebExtension context not found! ExtensionParent.jsm:778:13
21:15:54.309 Error: WebExtension context not found! ExtensionParent.jsm:778:13
21:16:23.331 uncaught exception: undefined - Exception catching is disabled, this exception cannot be caught. Compile with -s DISABLE_EXCEPTION_CATCHING=0 or DISABLE_EXCEPTION_CATCHING=2 to catch. (unknown)