Presonus doesn't make it easy to record an effect return, frankly. The manual is poorly provided with regard to recording returns.
The little information provided in the manual section 12.3.4
The solution to record in a DAW, an effects return coming from the 32SC or other series III consoles:
Before, first activate the desired tracks, direct them to an effect A, B, C.
Then, direction HOME.
Click on Audio Routing> Digital Patching> USB Sends.
Choose the output on which to record your FX return. Example: USB 41.
Assign a source to this output:
Here, do not choose FXA directly. But an auxiliary group Mix1 to 16 ....
For the example let's take Mix1.
This done, go to Mix1. Initialize Mix1: Use the next button until you see "FX RET A FXA" and the other effects returns (FX RET B, C ...)
Activate the faders of FX RET FXA to send the return to USB 41. Don't forget to activate the Master fader of Mix1.
In your DAW, initialize your source to be processed so that the effect return is captured on an audio track (input track 41 for the example).