If the red light is flashing your product is likely to be in failsafe mode which protects the unit from damage. Please follow the below steps:
1. Switch off the unit
2. Unplug the unit from the plug socket
3. Wait for 5 seconds and then plug the unit back into the wall
4. Switch the unit back on
If you have a ghd unplugged, the red light may flash if the charger is not plugged in correctly.