How can I repair my Stair Lift?

I have replaced the batteries in my Handicare Simplicity Stair Lift 950, because it was travelling both Up and Down at Low Speed. Batteries were brand new and fully charged.
Same result, Stair Lift still travelling at Slow Speed, and showing "n", on the indicater panel. Also noted that neither Remote Controls are working.
Stripped the lift down again to check that all connections were back in place. Reassembled with same result.
Any advice would be most wecome.
I am thinking of a possible Soft Ware problem.
Regards,
Paul Ballanger.