Can’t get REW to recognise my Focusrite Pro 40

Hi - Thanks for the add.

First time REW user here and I can’t seem to create a loopback with a Focusrite Saffire Pro 40.

No matter what I seem to try the REW software won’t recognise it.

Screenshot attached - The Ergo is my monitor control btw. I’ve tried to create a loopback from this with a cable and also from the Pro40, changing the REW input accordingly (and in my system settings) but still no joy. When I move to next section to play the sweep it’s not detecting a signal.

Any ideas what I’m doing wrong please?

Thanks.

Two days into this not working. If this is the issue I shall worship the ground that you walk on forever!