How is the Server/DPU configured? Did you add the DPU yourself or did you purchase a server with the DPU pre-installed?
For DSE to work properly, the DPU needs to be installed along with an additional card and cables connecting the card with the DPU for proper server integration and management. You also need to make sure you are using the correct BIOS type, BMC version, firmware and drivers per the VMware Compatibility Guide.
VCG
HW Requirements
If you did not purchase a "DPU Ready" server, Dell offers a customer kit for 15G servers to make them compatible for DPU/DSE.
Customer Kit
Hope this helps