This is a very recent thing I’ve had happening, presumably since an update. I will often have multiple FF windows open. In one of the windows, I’ll suddenly not be able to place my cursor in the address bar on any tab. But other FF windows function fine. I have to close that window and start a new instance or drag a tab from a working window to another screen, then that will work fine for an unpredictable time.
I have no idea what specific thing I might be doing that touches this off, as far as I can tell I’m just browsing. I thought maybe I had a child dialog opening in a hidden window, but it must be hidden pretty good because I can’t find it if I do.
Fedora Linux 42 KDE
Firefox 139.0
If this happens after closing a tab: Search the direct tab to the left of the previously closed one and open it.
I noticed similar behaviour when the tab to the left isn’t loaded at closing time. It also affects all other websites being unresponsive.