[GAMEPLAY] VelKoz ult (R) not working towards end of ranked game

I was playing in a ranked match with the Arclight skin. I want to say somewhere around 30-35 minutes in out of a 50+ minute match, my Ult just stopped working. When I pressed R, I could hear the ingame -click- sound, but it wouldn't ult. I switched the binding to a different key, and got the same response. I thought maybe dying would fix it, but it didn't. This is the only time it's happened to me.