In that case, there was likely damage to the ttl pin when you powered up the driver. Try switching over to pin 42 and cross your fingers:) Worst case is you’ll be out 10 bucks for a new mega board. The driver i used for the tutorial can’t be found anymore. It was much easier to work with and the power input was not polarity sensitive and could be connected either way. The board you’re using should be tuned with a diode test load as explained In the guide.