Im pretty sure your HDMI spitter is wrong. I initially bought this one but its not what you need. I could be wrong but I had the exact same issue with the black screen. This is what worked for me. https://www.amazon.ca/gp/product/B078YRDZKJ?tag=hyperioforum-21&ie=UTF8&psc=1
Also if you buy a powered usb for your grabber it seems to help a lot as well.