If you need to get started with discounts (promotion codes) today, then I recommend going with Event Espresso 3 and you can get in touch with sales to have your support license switched:
The support post ‘Discount Issues’ is closed to new replies.
Have a question about this support post? Create a new support post in our support forums and include a link to this existing support post so we can help you.
Support forum for Event Espresso 3 and Event Espresso 4.