A simple click on its blue button.... a simple refresh. But there's nothing simple about either. H.A.I button didn't appear on my toolbar, and FF's advice [go into safe mode...] didn't work either.
As to "simple refresh", that button doesn't appear in my FF40 either [and, again, when a setting shifts on FF it's basically unrecoverable, despite Mozilla advice to contrary].
I despair of Mozilla: it's like Microsoft, obsessed with sexy features at cost of basic operating simplicity/reliability.
Anyway, for an add-on writer to not assume worst [and include a hotkey] is naive. You shot yourself [and us] in the foot Mr. Erra.