So, today none of my users can reach FaceBook. I know of nothing that has changed. I suspect it has to do with Layer 7 blocking by country. FaceBook now owns 18.104.22.168\18 and I suspect that range is covered by one of the country IPs. Anyone have any thoughts on this. My boss has blocked almost all countries, so it's not just a matter of deleting a few and adding back to see which may be the offending range.
Might be worth a shot doing an NSlookup from a blocked PC to facebook.com and see what IP you get. Then put the IP in here https://www.iplocation.net/. May help pinpoint the country, if the URL is being resolved by somewhere in an offending GEO-IP range.
It was a country block. My boss blocks almost all countries. We do no do international business. With so many countries blocked, it was not feasible to remove and add back to determine which. Turned out to be Ireland. Unblocked (with much malice).