Machine is 2 years old - run for no more than 20 hours. Professionally serviced last year (£281) - used twice this year (max. 4 hours). Last used 2 months ago, driven into weatherproof garage for storage. Just charged battery & pumped up tyres, engine started straight away but when Motion Control Lever engaged no movement at all - neither forwards or reverse! (Blades will turn). What am I doing wrong - or what has gone wrong with the machine?