I practically reached endorsement level 2 only a few days after the update came out, and its only NOW that i get a notification congratulating me for it as well as a free loot box.
Is there a glitch? Was i still level 1 this whole time? How many does it take to reach level 3 anyways?
I randomly got 3 loot boxes yesterday so maybe to do with endorsement rewards issued retrospectively.
Zou get notified immediately in the chat when leveling up. The pop up window is the periodic reward you’ll get sometimes.
Oddly enough, notification and boxes don’t necessarily happen at the same time, and later on you just get boxes without being told for what. They just kinda appear. And the notification… I made a thread about that. That splash screen popped uo, telling me to keep it up - without telling me WTH to keep up. The actual level-up didn’t happen until after the next match after that.
With all that being so super secret and not explained anywhere, I can’t help but wonder. I mean… Whatever… Just gimme stuff. 
Not quite sure how the endorsement sytem works but im guessing it gives you a reward every month depending on your endorsement lvl.