Podcast setup: Mic One and Two work, Three and Four are not coming through

I am in the process of setting up my first podcast. My wife and I will primarily be doing it live recorded, but we already have some interesting guests that would like to speak in a live interview setting. I have 4 mics and am able to get 2 to populate and record in Studio One 3, but the last two will not populate for some reason. Youtube has been little help here. Below is what the interface looks like. I added input 1-4 as mono, but it will not let me add a mic to 3 and four squares so that they would be going in diagonal and line up with the inputs on both the x and y axis. Not sure what I am doing wrong.

Equipment:

********* UMC404HD interface

********* C-1 Mics (4)

********* HA400 Headphone Amp

Surface Pro 4 - Quad Core i7 6650U CPU @ 2.20 Ghz, 256GB, 8 GB Ram, 64 bit Windows 10.

Studio One 3 software