If you are sure that you have entered the promo code correctly, then the only reason it did not get activated is that the activation limit has already been reached. There are too many people watching the live stream and just a few codes to activate. Unfortunately, someone was apparently a little faster and had already used the code before you tried to activate it.

We understand how frustrating this must be, but don't worry. There will be many more live streams with promo codes and new interesting events to come :)