There are a number of possibilities. The two most common:
Your friend was referred by someone else, and that other referred got credit
Your friend had ad block software turned on such that the system could not track the referral (AdBlock and uBlock are web browser extensions that may interfere with our referral cookie tracking)
If another user made the referral first, that stands. The system is working as intended on a ‘first come first serve’ basis.
If tracking is absent altogether, then we'll work with you to confirm and apply the commission. Please get in touch with us on how to do this: email@example.com
Full referrals FAQs are detailed here: http://learning.firecracker.me/firecracker-referral-program-faq