Cause:
- the motor contactors are not detected as closed at the start of travel
- the motor contactors do not switch on
- the auxiliary contacts of the motor contactors do not switch
Remedial action:
- check the contactor monitoring
- check the wiring of the motor contactors
- check the supply voltage of the motor contactors 
- check the supply voltage of the contactor monitoring 
- check the "CO" parameter in the "Monitoring" menu