My new Rotak cable-electricity Ergoflex Lawnmower IPX4 TUP 3600HB1270.Bosch Registered . The Depth-of-cut lever will not move and my lawn is being cut to the roots! I tried pushing down, pulling up and pushing sideways, but the lever will not move! What do I do, please. I cannot see anything in the instructions! It was bought for about £150 from Amazon..