Have you tested the charger to see if it is putting out a charge voltage? Is there a fuse between the charger transformer and the motherboard or battery and if so, is it good? Are you sure the lift is on a ‘charging point’ of the rails? Is there a charge voltage at the charging point on the rails ? Are the charging points on the lift rails clean?
These are some of the questions I’d try to get answers to in checking out my Acorn if it exhibited the type of problem you described. One wouldn’t necessarily need a schematic to check them out.