Second monitor disappeared after 10.10.1

[DeeAtTheCrest]

Not only did the second monitor disappear, my Tricaster 455 no longer accepts output from the Mac pro after upgrading to Yosemite 10.10.1. What can I try?
Projecting from the Mac is why I have it.

 

[Partron22]

Projecting from the Mac is why I have it.

So downdate to the last version of OS that works for that purpose. It'll be several years at least before 10.9 or 10.10.0 gets outdated to the point of causing problems for iTunes, Apple TV or whatever hardware/software it is you're using for projection.