I've gotten an S- or higher in three games in a row with Nunu but I didn't get any level 6 tokens

I've been playing Nunu a lot, and since I got level 5 with him I've got an S- or higher for 3 games in a row since.

https://i.imgur.com/xRU2FX6.png

However, I still haven't received any level 6 tokens.

https://i.imgur.com/2I716C7.png

Edit: Somebody told me I can't get tokens from Nexus Blitz and it sucks because the gamemode is the only thing that makes me want to play this awful game.