Yep, it worked. Their booking system is horrible. Yes it's usable, but still leaves a lot to be desired. Had to restart the whole process to just change my reservation time slightly.

I did email them with the promo code error and they responded a few hours later claiming technical issues and they would happily credit me on the back end if I went ahead and reserved, so that's nice.

Been a few years but the economy lot is still nice. I'm glad they don't charge idle fees for EV charging (not sure they can with the long term parking model tbh.)