How do I repair my Tefal express generator steam iron?

I have a Tefal Express Generator steam iron and cannot get the green light to stay on it keeps tripping to red. I thought it might be limescale and have tried cleaning it but the green light trips to red each time.

The read light normally comes on to inform you that you have run out of steam but when I now fill it up it remains red. When switiching on the steamer it firsts goes to green then on heating it switches back to red.

When heating steam comes out of the iron until it turns red. Even when I press the button for Steam shots no steam emerges.

This iron is very expensive please let me know if I can repair this or refer me to a store to have it repaired. If you think I am wasting my time and should purchase a new iron please let me know?