Did u reach 6 path before Arena Rank monthly end?

If not that's what you get. It said in the game mail.

ok i understand that now.

You need to get the highest rank in this game to unlock rewards otherwise you are stuck at genin rewards.

That's really nice...

that's just a way to prevent non-spending players from ever getting a decent ninja from arena, though most of the ''strong ninja'' from are getting old now that jinchuriki have arrived.