your door lock latch assembly has failed, I would need to know the model number of you neptune to help you out better, but here are a couple of videos on the door lock mechanism. If you have a green cable inside the soap dispenser on the top of your washer you have this model. You can pull the cable to unlock the door.
Here is a video that shows you how to replace this type of latch. VIDEO
It is part number 22003593
or you may have this style neptune
here is a video showing you how to take the washer apart to get to the door switch
and here is a video showing how to fix the latch itself.
I will be glad to help you further if you need more help and if so please give me the model number off your washer, in the meantime:
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