Not getting mastery tokens

I've been playing league for a while and have only cared about getting a few champions to m5 because I like to have a diverse roll of characters and tend to practice for all kinds of team comp situations. However, recently there are a few champions I would like to reach m6 and m7 on. The problem is even after getting an S on a character, for example draven, I didn't receive a mastery token. This isn't the first time something's been wrong with my hextech crafting materials or items. Is this a bug and will I ever get my mastery tokens?