So I had this same issue with the Ricoh Theta V and just recently found a band-aid solution that seems to work for now until someone finds something better.
I looked around and started running through various Unity versions even ones that had been previously confirmed to work but they all gave that same pins error. I finally tried uninstalling the recommended UVC drivers that have been linked above and instead installing older drivers that @craig inked in this post:
The drivers specifically:
Windows 64-bit: https://theta360.com/en/support/download/liveapp4k/win64
Windows 32-bit: https://theta360.com/en/support/download/liveapp4k/win32
If you do this make sure to uninstall the recommended drivers or it won’t work. Then in Unity instead of trying to read the Ricoh Theta V/Z1 FullHD or Ricoh Theta V/Z1 4k streams, you will read the Ricoh Theta V FullHD or Ricoh Theta V 4k streams.
My current setup:
Using the skybox method
Unity 2020.2.4f1 (though I think I tested it on earlier versions and it also works)
Ricoh Theta V
Firmware Version: 3.50.1
Microsoft Windows 10 Education
(First time posting here so let me know if there is anything else that I should add)