If the door is locked using one of the screenless 2n Security Panels with a call button that look like this:
If you are using a Nelson Brothers 2n Security Card, tap your Card to the device.
If you are using the My2N Mobile app on your phone, press the dot with curved lines icon in the middle of the device.
The device should give an audible alert and the icon should turn green indicating the door has been unlocked.