The flashing light is to indicate the glycol tank has low glycol and needs topping up.
After topping up your glycol mixture, being sure to pour your glycol mixture slowly into the tank, replace the cap and wait a minimum of 5 minutes before turning the unit back on. This allows any air bubbles that may be trapped in the tank to escape. Trapped air bubbles can prevent the pump from operating correctly.
You will need to top up the glycol mixture for each additional fermenter that you link up.
For further information on this, please see page 10 in the Glycol Chiller instructions.
If the issue persists, contact customer support.