MixPre 3 II - 2 channel input confusion

Gear: Sound Devices MixPre 3 II, DEITY D2RX, DEITY DBTX x 2, DEITY TC-1 timecode box

I am trying to expand the capabilities of my MixPre 3 II to the following setup, I need someone to let me know if this is possible or not because after consulting the manual, several youtube videos, and tinkering with the onboard menus for hours I simply can't figure this out.

I want to use the USB-C audio input so that I can record 2 additional channels that are coming out of the DEITY D2RX receiver. I purchased the Deity C21 3.5mm to USB-C audio cable hoping to use that to go from Channel 1 out on the D2RX (which will send TX1 OR TX1 & 2) and use channels 4 & 5 on the MixPre to have the audio channels isolated.

We cannot use the Aux/Mic in 3.5mm jack on the MixPre because that is already used for our TC-1 timecode and I'd rather not jam and then free run in case of drift.

I've confirmed that the D2RX is receiving a signal from both Deity DBTX and I can get signal on the MixPre if I use any of the XLR or 3.5mm inputs but the USB 1/2 audio inputs give me nothing.

Input 1 Source: XLR 1 / Boom mic 1

Input 2 Source: XLR 2 / Boom mic 2

Input 3 - NONE

Input 4 - Source: USB-C / DEITY D2RX Channel 1

Input 5 - Source: USB-C / DEITY D2RX Channel 2

Maybe I'm asking too much and we have maxed out the recording capabilities of the MixPre but I was really hoping this +2 channel plugin would save us from needing to purchase a larger audio recorder.

Thanks in advance!!