I cannot connect to the CPU via the USB port

You have probably connected your PC to the CPU before installing the USB driver.
As for many devices, with Windows®, the driver must be installed before the first connection. Otherwise Windows® installs a default driver that doesn't match CPU needs.

- in Window® 's configuration panel, uninstall the driver attached to the CPU
- install the driver (from driver DVD, UnityPro DVD, or Unity Loader DVD)
- reconnect the USB cable between CPU and PC