Probably the reason that the PTO doesn't engage is because of the electronic clutch. The clutch has to have a certain amount of amperage to engage. I would reccommend that you connect a battery charger and charge the battery completely full till the charger stops, then the clutch should engage. As far as the battery, check to make sure that it is properly grounded. I'm not sure what could have caused the battery to drain so suddenly without something unusual making contact with the battery terminals. See if the battery holds its' charge after you charge it full; the bettery may need to be replaced.