Display resolution options disappeared after upgrade to Sierra

I purchase a new MacPro (the little black trash can) and shortly after, chose to install the Sierra update. Upon restart, it would not recognize my Apple Cinema's high res settings. After 3 hours with Apple tech support, they filed a report to Apple engineering who solved my problem with this solution:

• Shut down your machine
• Unplug all of your monitor's connections (in my case, 2 USB and 1 Thunderbolt) and reconnect using only the ports on the RIGHT side of the Mac.
• Voila! They said they are aware of the glitch, are attempting to fix it, and until now, this should work.