The reasons could be:

• Running frequency = 0.
• The motor is faulty, the load is too heavy, or there is a mechanical jam.
• The VFD has lost output phase or has an unbalanced output phase.
• The motor and VFD connection cables are severed, or the contactor (if present) connecting the VFD and motor is not closed.
• The control board is faulty.

How to resolve this:

• Increase the running frequency for the VFD.
• Address motor issues and resolve mechanical jams before restarting.
• Check motor and VFD connection cables.
• Contact the supplier for assistance.