Not sure how you missed this but someone posted on the forum that they face this problem : https://forum-narutoen.oasgames.com/page/show-post-23839-1.html

To simply what the post said, you have to be six paths first in one season, then the next season the rank you get (i.e. jonin) is the rewards you get. Until you get to six paths, you are stuck with getting ninja student rewards, which I think is bull.