I have a parity drive that Unraid disabled. I shutdown the system to check the cable, and when I turned Unraid back on the drive is no longer showing. All the solutions I could find involved being able to see the error'd drive unassigned if you stop the array, but for me it is not showing.

I previously posted about this drive here but I had not seen any warnings related to the drive since this post: https://forums.unraid.net/topic/197880-wondering-if-i-need-to-replace-my-parity-drive/

If the drive is not showing, it suggests it's not being detected or is dead. Swap both cables with a different disk and retest, you can also see if it's detected by the board BIOS.