Does the Macbook support displayport Alt mode over USB-C or Thunderbolt 3?

What MacBook Pro model do you have? What macOS are you using?

Every MacBook or MacBook Pro with a Thunderbolt or USB-C port supports USB-C DisplayPort Alt Mode.

The M1 MacBook Pro can only connect one display via Thunderbolt ports.

You may be limited to 8.64 Gbps if your MBP only supports DisplayPort 1.2.
You may be limited to 12.96 Gbps if your MBP supports DisplayPort 1.4 but not DSC.
Full HDMI 2.0b is 14.4 Gbps.
If your MBP supports DSC, it might not be enabled by default in Big Sur.

The CSV-1593 contains a DisplayPort MST hub to support multiple displays but macOS only supports one display from an MST hub. However, macOS can use the MST hub to convert fast/narrow DisplayPort (HBR3 x2) to slow/wide DisplayPort (HBR2x4 or HDMI in the case of the CSV-1593).

I suppose first thing you should do is to use a different display, USB-C port, OS, and/or  computer to verify that the CSV-1593 works at all.