So you are dealing with a finicky lawn tractor that doesn’t want to start when you turn the key?
That is not uncommon and should not surprise you because it is a machine and every machine will breakdown from time to time. A machine is only as good as the quality of its parts and the maintenance that is performed each year.
Let’s check some easy stuff first.
Is the battery fully charged? Does it have at least 13 volts? Do you have the lawn tractor in neutral? Do you have the clutch pedal fully depressed?
Are you sitting in the seat so the seat switch is engaged?
Those are the most common problems that cause a lawn tractor to not start. The other not so common ones are that the main fuse has blown. You can check it by finding it under the hood or near the transmission area. It is normally close to the battery. If you find the fuse has blown, replace it with a new one and that will probably fix the non starting issue.
Continue to check for power to the starter if it doesn’t and if there is power to the starter, then most likely the starter is bad. Replace it and test the lawn tractor for proper operation.