After doing more experimentation, and research. My guess is that CPS2 has a really weird resolution (512×262 after overscan) and digital upscalers don’t know what to do with the sync signal?
Trying it with yet another monitor gives “invalid resolution”. And since this is a Retrotink section i’ll reiterate that retrotink 2X gives a blank screen when used in conjunction with RGB2COMP (Again, i’ve tried many combinations, but i’ll stick to Retrotink products). Is there something out there that can trim/pad the video signal to something more standard that upscalers/LCD monitors are more likely to accept?