did you try using other resolutions to see if you get an image in any of them ?

mmm... did you try changing the "signal" in your capture card properties ?
Like for example, switching from PAL to NTSC-M or anything like that ?

I have this issue too. Sorry to bump an old thread but I'm really desperate for a solution. I'm getting that same gray background with gv-usb2 selected and the same settings. If you or anyone else have since figured out a solution, please let me know.

The only solution I can think of is to do a Screen Capture instead of Video Capture Device and zoom in on that segment of your screen 🙁. Sorry, this is easiest fix off the top of my head, though not optimal.

Do you have the right video signal selected under "Configure video"?
My GV-USB2 defaults to Composite and I have to manually switch to S-Video.
It should work on the default settings; no need to tinker with those. If it doesn't then there's only guessing left. Do you have the most recent drivers for your operating system? (The ones that come on the Mini-CD are outdated and you can download the most recent ones online if you provide the serial number of your device) Other than that I can only think of broken cables or a hardware failure of the device itself (does it work with AmarecTV?)

Worth adding that I had to use the 32bits version of OBS Studio to get any image out of AmarecTV with OBS Studio (even though my PC is a 64bits operating system).

I haven't tried it standalone but it could that this may be the same case. Worth a try.