We are using a MacBook Air running OS Mojave v10.14.6 on a Promethean Active Panel i Series (S/N GG182000003410 ) running version 188.8.131.52 of the Promethean software.
The HDMI port in use is the one closest to the power switch on the OPS unit.
The screen capture results in a black screen regardless of what is displayed on the MacBook Air (e.g. PDF document, home screen, etc). When connecting to this Promethean via AirPlay the screen capture works as expected.
Promethean Tech support says this is an Apple HDCP problem. I can't find anything relevant in Apple Support. This combination has worked in the past and has only recently been acting up (where the screen capture function of the Promethean consistently results in a black screen).
I'm at a loss .. . .