It could be that the door key has broken, or maybe even the button that opens the door could be broken inside the unit.
If it's not doing anything there could be a blown fuse inside from the switches not being operated correctly.
You can open the door by sliding something very thin like a plasterers wet knife between the door and the cavity and pushing up the door key if it isn't broken.
If it's a built in unit, you'll have to get it taken out so it can be properly inspected to see what the problem is.
Jon, October 2014
