Lots of potential causes.
What do the other statuses show?
- On the cRIO
- The cRIO power light (by the power plug)
- The cRIO status light (below the power light)
- Digital Sidecar
- The tiny RSL LED directly on the Digital Sidecar (by the power plug)
- The three power lights all bright green?
- The status lights on the speed controllers are blinking I take it?
- The other Driver Station Diagnostic indicators
- Communication
- Robot Code
- Other Diagnostics, e.g., cRIO?
You said you were able to Enable the robot, and that'd only be possible if the cRIO were running normally. If that's true then
- Digital module in slot 4?
- You can try pulling the breaker for the digital sidecar to see if the 5v light glows but the others go out. That'd mean the Sidecar was getting power through the 37-pin cable.