Just helped someone on F38 Plasma with this, after updating his pinned Firefox shortcut in the Task Manager, suddenly did not launch Firefox anymore.
After the last update of Firefox 118.0.1, there are now 3 different Firefox entries in the start menu (Application Launcher), Firefox, Firefox on Wayland & Firefox on X11 (at least in Plasma there is). The only one that will start Firefox is the Firefox entry, so he had to unpin his old Firefox entry, and make a new one from the Firefox entry in the start menu.
So i guess you have to delete your old desktop shortcut, and make a new one for Firefox to launch again.
Hope this makes sense…
EDITED 071023 - I misunderstood the feedback i got from the person i tried to help, so this is not correct:
“so he had to unpin his old Firefox entry, and make a new one from the Firefox entry in the start menu.”
“So i guess you have to delete your old desktop shortcut, and make a new one for Firefox to launch again.”
This is going to be broken until firefox-118.0.1-7 is published. (It’s currently building.)
firefox.desktop improperly added DBusActivable=true, which is causing Plasma to crash due to a bug in its error handling. I’m not sure what GNOME does; it may just ignore the directive as invalid.
The extra Firefox on Wayland/X11 entries will also be removed in that update. Ironically, they can probably be used as a workaround if you install firefox-wayland or firefox-x11, respectively, which are the packages they’re supposed to be in. Those secondary .desktop files don’t have the directive that is causing breakage.