I would guess tracing the wire that goes to the clutch switch, sounds like it's not getting thru now. Do you have a manual with a wiring diagram to see where (and what color) you could do a continuity test ?
You might also check the the little button switch itself to make sure it wasn't damaged during the change over. It's not as vulnerable as the brake button but still might have gotten damaged.
One of the electrical experts like Hoople will be along shortly to help you more.