Two mics connected through audio box, channels set in multi-track, but Audition is only picking up 1

Hi !

I am doing podcast recording and using a two-line audio box (I have a PreSonus AudioBox USB 96 and a M-Audio M-Track Duo). Both boxes are having the same issue when connected. I have two AKC P120 Mics that are connected in Line 1 & Line 2, the box is plugged via USB to my laptop. I have the channels set as follows:

As you can see - Even with the individual tracks input set Track 1 to Line 1, and Track 2 to Line 2, they are both picking up Mic 1 only. Does anyone know why this is?

Both mics are functional and I can see the input lights flickering on the box for both Mic 1 & 2, but Audition can't see the Line 2 mic? Any help appreciated - I have been trying to find an answer for weeks!