Using tiers on YouTube Live

Hello! How do I use the different tiers within a YouTube Livestream?

Example, I have two different membership levels. On is called ‘economy class’. The other is ‘business class’. When I try to setup alerts to have it say; 

“John Doe has been a Business Class member for 3 months.”
{user} has been a {tier} member for {amount}.

, it doesn't work and the alerts simply don't show up. Am I doing something wrong?