Which loco is it?
Some of the ones I have with flywheel motors connect to the bogies via 'power rods'. These rods can become disconnected from the motor if the box gets knocked about, and the symptom is usually exactly what you describe.
Pry off / unscrew the body and take a peek - you should see the connections are off / loose. Should be a simple enough job to pop them back into place and you'll be underway again
Looks good - what radius / size points are you using in the plan?
The Bachmann sheds are stunning, and could look well as the backdrop to your station - do you plan a fueling port, or what facilities at the depot?