Welcome to MTF. I love the old steamers so lets think about this.
Holding the engine, you should be able to spin the wheels. This will rule out any rod problems.The rods also push a bar for the steam unit.
Are you referring to the engine light?
Does your engine have smoke?
Smoke makes it slightly complicated but it also has to move (chuff)and cannot be stuck or jammed.
The simplest is when you set it on the track all wheels must be aligned. Cause if the front pilot wheels aren't, it will short and the red light will show on the transformer. Make sure the track isn't shorted with a screwdriver . Very common problem.
I checked you do not have smoke but you have magnetration. Look at your drive wheels and axles and make sure you have no metal pieces shorting anything out. I know it's spotless but check.
Next put the engine on it's side and try to start it with two wires from the transformer. One to the center wheel one to the outer and listen to the click of the e unit. If it runs it should be ok.
Next the e unit look at the drum and see if it spins and the little finger contacts look good. Little fingers do not like to be poked leave them be.You want to be sure the drum didn't break at the ends.You may see enough of the eunit without removing anything.
Last scuff up the wheels and track and the small center rollers.
Do not over oil the motor.
This is the basics too bad you don't have a second engine to run the track.
If you find something send a picture.
Read the SPECIAL Basic O/ O27 manual it will help and is a good reference.
Since your bulb is out, the center feed wire from ther rollers could be broken before it reaches the e unit.
If all this fails we need to remove the shell for a better look.