Check your 3 phase supply. Check it from mains to MCC Contactor and isolation transformer to the drive.
Also tell me when you are getting this alarm. Is it immediately after Power ON or is it after the emergency release.
Also what is the message on the CNC Screen.
(1) Meaning
In the main circuit, the DC voltage (DC link) has dropped.
(2) Cause and troubleshooting
(a) A small power dip has occurred.
→ Check the power supply.
(b) Low input power supply voltage
→ Check the power supply specification.
(c) The main circuit power supply may have been switched off
with an emergency stop state released.
→ Check the sequence.