Then it sounds like the roboRIO is operating and communicating with the DLink. So it might be an incompatibility between the roboRIO and PC IP addresses.
So among things that could be wrong:
- Ethernet: The DLink isn't serving DHCP addresses, and/or the roboRIO/PC have incompatible IP addresses/netmasks. You can check this on the PC using ipconfig or checking what the PC network adaptor's assigned IP address is.
- USB: the PC may not have the USB network running, i.e., FRC Update package not installed, crashed, etc.
- Both: the PC mDNS resolver may have crashed. Rebooting usually solves that, but you can check in the Task Manager to see if the service is running.
Since apparently you say that the Driver Station Diagnostic ping's aren't seeing the DLink, then the problem is between the PC and the DLink.
Most likely the PC has issues, since it should see something.