We started getting this error after our network administrator switched
us over to our new FortiGate firewall. Apparently that changed the
external IP address of the requests from our JSS, and Apple had to
whitelist the new IP address. I got help from...
Thanks for the tip @agetz! I was also able to solve this by booting into
Internet Recovery. Here are the steps I took:- Restarted and held cmd -
opt - R to boot into Internet Recovery (as @agetz stated, regular
Recovery wouldn't work; it had to be In...