Reseat the the connection for connectors P3, P4, or P5 on the I/O PCB.
Measure the voltage across the red and black cables.
Press [EMERGENCY STOP]. There should be no voltage.
Press [RESET] to clear the alarms. The voltage should be between 20-30 VDC.
Examine the connection at the motor's brake  and power connectors  for contamination. Reseat the connections.
If no voltage is present, refer to: