There are two places you need to “route” your audio.
First, you need to route the audio in/out of the console. If you are using channel “inserts” then this is where you want to route this audio. For example, if on your Vocal 1 channel you want to route audio out to the Superrack Performer software and back, you’ll need to example route the insert out of USB1 (or whatever output you are using) and then back into the insert also on USB1 (again substitute this example for whatever input you are using).
Second, the software you are using to host the plugins (Waves Superrack Performer) will also need to have audio routed correctly. For example, if you want to use Rack #1 for the FX on Vocal 1 channel, you need to ensure that Rack 1 is set up to use USB 1 as it’s audio I/O source. So USB 1 input (which is really the console’s USB 1 output) goes into the Rack, and the output gets sent out over USB 1 output (which is really the USB 1 input on the console).
Hopefully that makes sense. Long story short, you need to check your routing on both the console and the Waves software to ensure it is set up correctly.