There should be a fuse for the step, which may be blown. Open the driver's door and look for the fuse panel in the driver's seat pedestal. All Airstream-installed components that operate from the chassis battery (step, awning, etc.) have their fuses in that panel.
But a stuck step isn't the end of the world. The van remains perfectly driveable; you just have to make sure you don't scrape a curb with the extended step.
Engineering: Finding complex solutions to simple problems you didn't even know you had.