All good to go. Firefox is now cooperating.
So was the problem in the Custom CSS or the Extinct Child style.css?
(I cannot see reply #2688, so I suspect it was not for me.)
Really appreciate you getting in there for me and resolving it.
I have a lot of patience and can usually figure this stuff out on my own, but this was truly dumbfounding me and felt I had to ask for ask for help.