[frfl]

Ran into same issue. What worked was the first email that gives you a link to gumroad. After using the coupon and providing an email to gumroad, it showed me the confirmation page, but didn't send me an email for the PDF. The fix was to go to that gumroad confirmation page, and where it says "enter a password" (basically it'll create a gumroad account) you'll then be able to login and check your gumroad account, book should be there.