No need to worry, man! I'm new to MMM, but I definitely used the link and the credit showed up in my account right away. I haven't seen the other credit from my link being used yet, so I'm guessing there's some sort of delay to prevent someone from using fake accounts to build up credits (or it's due to the SIM issue m8547 mentioned - I'll try to remember to update if/when I see the credit).
I wish I had discovered MMM and Ting a long time ago. Sprint has been a huge pain to deal with over the years, and now I can finally use my old Sprint phone after cancelling my account because of their terrible service.
A note to other newbies: If I could do it over again, I'd scroll up the list and give some love to the people who got skipped. Maybe someone could create a rolling list of the links that haven't been used yet?