Did you do all the previous suggestions?
Is it setup with only the RoboRio and PDP?
Are the Can cables installed properly?
Is the termination jumper set correctly?
What firmware revision is installed on the PDP? RoboRio?
Browser you are using to access the RoboRio webdashboard?
You might want to read through the links I posted earlier. This one specifically
http://wpilib.screenstepslive.com/s/...ribution-panel
You will want to look at what sticky fault is being logged to help narrow down what the issue is.
Post some screen shots of the self test results.
Hope this gets going for your soon.