Stannah hinged rail will not opperate. ?

Hi, I have a model 300 Stannah hinged rail lift and I am not able to get the rail to power up or down. I have to move it by hand so that the chair will work. Two days ago in an attempt to get it working which it has not for several months I took the boxes off the bottom of the rail to see if there was a broken wire or something and noticed that the switch on the last one was turned off and when I turned it on the rail worked fine but today it does not work at all and the switch and light are still on. Can you advice?
thanks,
Ed