Maytag Neptune Displaying Error Code ND?

My Maytag Neptune is 7 yrs old. I am getting a "nd" error and the door is locked. How can I unlock the door? I had a repairman out over a year ago, he told me what he did was make sure the door would not ever get stuck being locked. Well it's locked. Help! My autistic son keeps yelling at the machine, he's 24 but does not cope well. I have got to get this machine door open.

No there is no string to pull. I can't think of the exact model number, but it's a Neptune front door, low water consumption. I pray this isn't very physically taxing. I couldn't watch the repairman at the time, so I don't just want to mess with something with the computer panel. Thank you in advance for your prompt response.

By Anna C