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Some USB-C converters / hubs are the problem; they don't allow proper communication with the hardware. In our testing we've found that typically the more expensive USB-C-to-USB-A hubs (or adapters) were the ones that worked properly, but the cheap Chinese ones did not.
You may also consider testing with a USB-C-to-USB-B cable to connect the mixer directly to the computer, thus narrowing down the hub as the problem.