Travis - Recommend proceeding as follows:
1 - Check (then check again!) to make sure the wiring is correct. Since your H has a 4-position light switch, the tractor was orginally equipped with a cutout relay. Since it now has a voltage regulator, the wiring has to be modified slightly to accommodate the regulator. Punch below for a diagram of how it should wired up now.
2 - Make sure the regulator is solidly grounded. Run a temporary ground wired directly from the regulator mounting base to the grounded battery terminal.
3 - Repolarize the generator. Momentarily connect the BAT and ARM terminals at the regulator with the engine off. Soon as you see a spark you've successfully polarized.
4 - Start the motor and run at 1/2 throttle. Temporarily jumper the BAT and ARM terminals at the regulator. If the ammeter now indicates charge, the regulator is bad.
5 - If still no charge, temporarily connect a jumper wire between the generator "F" terminal and a good ground. If the ammeter indicates charge, once again the regulator is bad. Otherwise the problem is in the generator.
Note: Since you now have a voltage regulator, the light switch no longer has any effect on the charge rate. The L and H positions are simply two "off" positions for the lights.