A model number might help

I believe you are talking about the door switch activator.
There is a switch inside the machine that must be closed for the unit to run.
If it is a little clip that has bust off snaps into the door, you will have to replace it.
If it is a metal actuator you may be able to re-bend it so the door closes the switch, just be gentle. The actuator is often mounted to the switch which is plastic.