After ripping it out and installing the latest version from scratch everything worked perfectly.ītw - I use AppZap to clear everything out, because in my experience Blackmagic's own Uninstaller can't be thoroughly relied on to strip everything out. and Desktop Video and Media Express didn't work. Not thinking, I upgraded the OS to Sierra. I recently acquired a new Mac Mini simply to serve a SD videotape capture flow using Ultrastudio Express (hardware) Media Express (software) on top of El Capitan which was pre-installed by Apple. Then I had a brainwave - completely clear out all BM installed components and install the very latest from scratch. I have four MacOS systems running various BM hardware - all controlled by Desktop Video and using Media Express - and I've pulled lots of hair out trying to get ME to work properly after an OS update. One thing that I've learned lately (yes, it's taken a while!) is that when you upgrade the MacOS it's really important that you completely and utterly uninstall the existing installation of Desktop Video and all the installed Blackmagic components.