This looks like a small bug: Taking screenshot in the iOS app only saves a black box to Fotos,
For me yesterday also, the days before it still worked.
Same here while I was in running mode.
Interesting fact. It works when you open the app and you did not start to run / ride. But when you are in full swing - I am getting the black image.
I am getting the black image *and* the image I wanted to take. This happens when using ZML to take the shot on iOS but running Zwift on Windows 10.