Since updating to OSX "El Capitan" and Office 2016 I am having trouble recording my lectures. When I switch my Powerpoint presentation to display mode, the beamer screen goes grey (although I can see my presentation on my own laptop). That can be "solved" by disconnecting the displayport cable and plugging it back in again. If, while presenting, I want to switch to some other application for a while (say a browser or some other program) then as soon as I return to Powerpoint and start displaymode again this gives me the same gray screen on the beamer. Needless to say, all this simply worked before I upgraded both.
A sloppy workaround would be to first put my Powerpoint presentation in display mode, then connect the displayport cable, and then to remain in display mode throughout the lecture. But even that does not work, as I am recording a screencast with Camtasia in the mean time and this also leads to trouble: either a "screencast" with just the initial display screen (but working sound), or a screencast with working sound and the beamer image somewhere on the right of my screen, distorted.
I have tried a couple of different things, including using Screenflow instead of Camtasia (does not help). Finally, I found a workaround that I can live with while I wait for the setup to just work again:
I can then switch back and forth between the Chrome output (=my presentation) and other software - works like a dream. The only issue remaining is that if I want to switch to a browser window during the presentation, it is easier to open a separate browser for this (for instance Safari).
Not sure what exactly is causing all this, but a big thanks to Microsoft and Apple for not testing through whether the newest OSX and Office work well together.