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

Ed
November 2014