A GREY radar icon indicates the sign does not have a radar unit attached or the sign was unable to detect the radar unit. In case of the latter, it could indicate a hardware or wiring issue.
A RED failed icon indicates that the controller did not detect a radar unit but received a radar setup command and failed to enable the radar. This could be a hardware or a wiring issue.
Before ruling it out as a hardware issue, lets try a couple of soft steps first.
Send the sign a DISABLE radar command from DS-Live and then restart the sign by pulling the main equipment fuse, waiting for 10 seconds and reinserting it.
The radar icon in DS-Live should then show a YELLOW icon, which indicates radar unit is detected but not enabled. This is a good indicator that it is not a hardware failure.
From DS-Live, send the sign a valid radar setup to enable and use the radar unit. If successful, the icon should go Green.
OR
If the icon is still Red after the above steps then it could be a hardware failure.