The red wire is intentionally not connected because it is absolutely not required for operation. However, to stay compatible with the PWM standard spacing and connection order, the red wire was left intact.
There is plenty of documentation at vexpro.com on the Victor SP in order to assist in debug.
The Victor SPs are 100% tested before shipment so you, most likely, had an issue with connecting it to the Roborio.
You probably do not need a replacement, jut need to undo whatever the electrical mentor did inside the product.
If you need assistance with any VEXpro product you can always e-mail
prosupport@vex.com or call us at 903-453-0802.
Paul