I speculate that the USB-C implementation of the DAC is defective, specifically for USB-C cables that have E-Marker chip. For context, the USB-C standard requires that any cable that is able to deliver over 3A has to include an E-Marker chip, and some devices, potentially the SU-6, are designed in a way that doesn't support these cables. The DAC may still connect over USB-C if the cable doesn't include E-Marker (which is optional for cables that are designed to deliver 3A or below).Might this be a legitimate reason? https://www.reviewgeek.com/105739/googles-pixel-6-is-disappointing-audiophiles-heres-why/
I am experiencing the same issue when trying to connect the DAC to my Mac. Unfortunately, I cannot verify this theory since all my USB-C cables are cable to reach 100W (i.e., 5A), but this is a relatively common design issue with devices that support USB 2.0 speeds while providing the USB-C ports.