When you have collected 35 stars you will get a reward. The reward is similar to what you used to get in the end of episode chest, so will be boosters and free play time.
Hi @manxmano - you should have the chest in between events (for example it does not show when Petopia is on or when you have the 1,2,3, Grow Pet event)
Can you please show a screenshot of your game?
What do you see here instead of the chest?