You are right that this is OT, and should have been marked as such.
But, since this is bouncing between which app has an error, I'll toss in
that it may have nothing to do with either app, but with the DNS server
that each app is using. If the site's new certificate hadn't yet
replicated to the DNS server that Firefox used, but did to the one
Chrome used, this is exactly the result one would get.