Promo Code for Universal app can NOT be redeemed on an iPhone

I have recently developed Puzzle House: Mystery rising. Originally, it was on iPads only. About 2 weeks ago we submitted a new version that made the app work on iPhones. This version was approved yesterday. Today, we want to get the word out and so are testing the promo codes that come with the new version. However when I go to use a Promo code, I get the following message. The code was typed in.

I called the Apple Developer support team and they said everything looks fine from their end: They look for two things 1) The app was built as a Universal App and 2) the Promo codes are still valid. We passed both of these. I'm trying to get a hold of the iTunes Store Customer Support Team, but email is said to take up to 48 hours. Any ideas on a phone number 😉

Has anyone seen this issue before?

Thanks in advance!

-Curtis