It has been reported that the recently updated Instant Play plugin does not work on this latest version of the popular web browser even though it is not shown on the list of exentions that will stop working unless they are updated.
If you have already updated your version of FireFox don’t worry as Game Maker Community adminsitrator Chronic has discovered a fix:
This version doesn’t seem to be a compatibility issue, its just a problem with the maxVersion variable found in the install.rdf file. I altered this and it seems to be working fine for me now.
How i fixed it:
Download the addon (YoYo.xpi, right click, save as.)
Rename from YoYo.xpi to YoYo.zip
Unzip to a new folder
Open Install.rdf in Wordpad
Find this line: em:maxVersion=”3.0.*.*” />
Change it to: em:maxVersion=”3.*” />
Once you’re done with that close and save the file and rezip all of the files in the folder and rename it to YoYo.xpi then drag it in to a firefox window to install it (uninstall the previous version first).
Now, i’m not sure that this will 100% fix the issue, but its working for me. So do this only if you must, otherwise wait for an official solution.