hayter heritage 10/30 starter solenoid?

Then you may well have done something wrong...

The solenoid should have a big wire from the battery and another big wire to the starter motor - it's just a switch after all - there should also be another wire from the ignition/start switch to make it operate. This needs a return path to the machine's chassis for the solenoid to work.

The battery also needs to be well charged up for things to work.

The starter switch needs to be working properly
The engine should not be seized up

Listen for the solenoid to click when it operates - no click = not working.

Good Luck...
May 2016