Was it working at one time but it's broken now, or is this a new installation? Do the points move freely if you push them by hand? Have you tried removing the Tortoise and testing it by itself?
I'll agree that you've probably got some gunk in the Tortoise, but you should check the easy stuff first.
It takes an iron man to play with a toy iron horse.
Sounds like you may have some dirt in the gears inside!
If the Turtle Machine is out of warrenty
There are 5 screws under the sticker on the side
Just remove them and take a look inside!
If there is dirt in the greas - clean it out and relube the greas!
The Turtle machines are pretty sturdy units!
Our Club had about 20 of them survive a fire - lots of smoke damage and ash!
I took each one apart - cleaned out the dirt and relubed the gears and they are Still working today on our Lionel layout on the custom turnouts we use!
The fire was back in 1990 - so the Machines have been in use a lot since then!
BOB H - Clarion, PA