For a while now we've been seeing the no entry sign in Firefox, both when using one of the auto-update scripts or when I install through AutoPKGr.
Any thoughts of what could be wrong?
Likely a permissions issue. You could verify through the terminal and looking into the application.
I had the same problem, but after completely uninstalling Firefox (I followed this manual https://www.youtube.com/watch?v=Pvt580LIMMY&feature=emb_title) and reinstallation it worked again. Don't ask me why though.