If you've earned enough Stars through logging in, yet when you attempt to claim your Star Reward, you receive a message that says, "You haven't played long enough to collect this!" it means you have not spent enough in-game time within Adopt Me to claim the item.
We have implemented a play-time limit to ensure these rewards are meaningful for players' hard-earned efforts of logging in and playing consistently. This play-time limit means players can't log in to all of their alternate accounts and gain the rewards quickly, as this would ruin the value of the rewards due to them being easily obtainable. As such, when players log in to claim their reward, they must have played Adopt Me for a set amount of time.
You will need to play Adopt Me for a few hours to receive your reward; in fact, you'll need to have played 90 seconds per Star needed to claim. For example, you need to have played 12600 seconds, or 3 and a half hours, to claim the Human Bubble, which is worth 140 stars. The following chart details the number of stars and subsequent play time required to claim the items.
To get the Golden Egg or Diamond Egg, you would need to play for 16 and a half hours over 180 days.