My Fellowship finished a stage, but I didn't get any rewards. Why is that?

To benefit from your Fellowship's progress in a Fellowship Adventure, you will have to participate in the Adventure as well. This participation is considered per stage, so you should make at least one contribution to any Waypoint in a stage to receive the rewards at the end of that stage. 

Example: if your Fellowship completes the first three stages, and you have invested in Waypoints during stages 1 and 3, you will receive the rewards for stages 1 and 3, but not stage 2, because you haven't contributed to the progress of that stage.