Poulan 38" riding mower.

Battery is likely dead - or has built a sediment bridge - shorting the anode and cathode.
Jump-start the tractor with your vehicle - or another battery to check.

Or - use a multimeter to ensure your battery is not draining to 0V when you attempt to start.
This also indicates a failed battery. It may have a decent float charge - but when the load starter) is applied - the voltage will drop right out.

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