My picture when out and the green light came on

Make sure you replace the door to lamp back on the set, as the unit will not work if the door is not reinstalled. This is a safety feature.
Make sure you reinstall it correctly and securely. If this still does not work, then you might consider replacing the ballast also. It is the usually called the lamp driver. Its used to light the lamp. When you cut on the set listen closely near the lamp housing for slight clicking sounds, this is an indication the ballast is trying to iginite the lamp and that its ok..