There are a number of reasons this could happen.
The most common mistake people do, is not correctly tag their uploads. Its important to include your artist display name in the correct place to ensure it appears on your profile. For the different type of uploads, the location can change. Please see this article for more information.
First please check that the file has finished transcoding. This normally takes 30-60 seconds for a 5 min track, and 2-3 minutes for a longer 60 minute mixtape.
There are some instances where the transcoding gets stuck. If your track has still not appeared after 10 minutes, please contact us firstname.lastname@example.org.