I'd guess that the stoker mechanism or the blower is blocked, or rusted up from sitting all summer. The reset button is popping because the motor is overloaded or is stalled. Or possibly the motor has gone bad and needs replacement.
Have you given the unit some regular maintenance like oiling the motor [if it has points to add oil] check the gearbox oil level, and the pusher pivot bearings.??
Check to see that the bed of the stoker moves freely, that the blower doesn't have a mouse nest inside, or other obstruction.
Make sure you don't have a couple of big pieces of coal or pieces of rock jamming the pusher block. You may have to empty the hopper and start with fresh coal if you have some too-big coal in the hopper.
Hope this helps. Greg L