It's mounted now but disabled. Seems like my next step is to pull the drive and check the data on another PC, then, if I'm confident it was only a cabling issue, I can:
Stop the array
Set the disk to be not installed
Start the array
Stop the array
Set the disk to be the appropriate disk
Start the array
My Unraid does not hold valuable data, so I feel comfortable risking it. Though perhaps I will RMA it through WD since it's 1 year old.
tower-diagnostics-20200706-2208.zip