I have the same problem, both with a GoPro 7 (stabilisation turned off, 1080p 25) and a a Canon R (set to 1080 PAL) and I can't get both to work.
With Desktop Video setup, it can see the inout but there is no output. Also Blackmagic Media Express can't detect any input. This is with 11.5.1
I have a camera monitor and it is detecting the signal from the Canon as 1080p 50hz.
I uninstalled 11.5.1 and installed 11.4.1 and then at least Media Express would recognise the unit but wouldn't see any video signal.
VEEEEERRRRYYYYY FRUSTRATING