Trains are stupid!

I've been chasing this problem for a couple of days now.
The decoder wasn't responding. Couldn't load the sound files or do any other programming.

Thought maybe I had a bad decoder.
Maybe the plug connector between the engine and tender was faulty.
Wrong wires connected in the wrong order.
Nope, nope, and nope.
Finally found the problem just now.
The tender trucks were turned around.
Sigh.