Hi. The Bach man replied to my similar dilemma. Our set used to work but not this year. I found the connecting wire under one piece of track had broken loose and I found the small gap in one rail on the last straight end piece had been pushed together. If your train runs in one direction: while its running dissconnect the end track and see if the car reverses.
James2

Thank you Bach Man! I was not sure if you mean the last full straight track  (with the arrow pointing to the bumper and away from she, or the little bumper track itself. I found both pieces of track had rail joiners on both sides. Removing the joiner from either one did not fix the problem BUT in removing one from the straight end track I found one piece of the rail pulled off. When this is replaced leaving a small gap the reversing trolley works fine! 

Our reversing trolley only runs in one direction. It will go from end track to barn. when it gets in the barn, if you pull the end track off it will start up and run towards the end. If you put the end track back on  it it makes car reverse. Any ideas how to fix this? Is it a problem with the shed mechanism? Thanks!