Hi Linda
it sounds like the up limit switch is stuck these are switches that only stop it going up, the stairlift has a series of safety edges, which are located on the footplate,carriage. these stop the stairlift from bumping into things and also for stopping the lift at the top and bottom in its correct position. Check they are all free and not clogged with fluff if a switch is activated it thinks its at the top and will only go down.
The reason it stopped at the bottom is it went to the top the switch got stuck or broke and then you went down with a broken up switch and stopped at the bottom if you need any help just reply
Gazza
April 2012