Powertrek TX1000 not working?

The running machine was working fine, but the last time I ran, the speed would not reduce at the end of the run, using the speed buttons, and I ended up having to jump off and switch off by the mains as even breaking the magnet connection didn't stop it. What could be causing this and how do I fix it? All the lights on the display come on when you switch on but the belt doesn't turn or the switch start.