There are generally two reasons for this:
Reason #1 - Your graduation year is missing. Without this we won't know which class to rank you in. You can fix this by logging in and updating your graduation year.
Reason #2 - You may not have enough times to create a Power Index. You need to update your profile to make sure that you have times from two distinct events. Once you have, we can calculate a Power Index for you.
While Power Indexes are updated immediately rankings are updated overnight so check back tomorrow, and all should be well.