I have a supplier using the DK-DEV-5CSXC6N. Using the on-board USB-Blaster circuitry they can successfully run debug sessions on both the HPS and the FPGA. However when using an external USB-Blaster not so much.

USB-Blaster II (https://www.digikey.com/products/en?mpart=PL-USB2-BLASTER&v=544). My supplier has two and tried both getting the same results with both. They tried a 1M clock with the same result. The supplier stated "I believe we tried changing the speed at one point and it was not successful. I just tried again and once again have not been successful. JTAG speed is reporting back at 1M".