I have a 27" iMac w/Retina display, OS10.12.3. Running a Panasonic BT-LH 1710 Monitor from the Thunderbolt output to DVI cable. For quite some time I was able view the sequence full screen on Panasonic, I do use the monitor on location from time to time and at some point after reconnecting it I lost playback. It acts as a 2nd monitor for the mac but I can not get it to work as a full screen playback. It shows up in PP playback preference, I have "Enable Mercury Transmit" checked, I've gone to the Mac's monitor preference and tried different resolutions, tried different sequence settings but nothing has worked.
Never mind... Ihad never change resolution on the Retina display, just went to that and selected the next larger text size... (funny it didn't speak in terms of size/resolution) but now I;ve got my monitor back.