Do not upgrade your computer to an OS that is newer than your Avid Media Composer is qualified for.

10.10.5

10.7.5

10.13.3

10 Pro

10.12.6

10.8.5

High Sierra

See the list of all recent versions of Media Composer:

10.11.6

10.9.5

10.13.3

Lower versions of OS X and Avid Media Composer still work great (and often better). Click on these links below:

High Sierra