Aternos has many users around the globe. Unfortunately, we are not able to serve all users at the same time, because our resources are limited. Because of this, we have to stop empty servers without players.
You've probably noticed the small timer in the left corner of the green bar on the server page:
This timer tells you when your server will be stopped to free up the allocated resources for another user.
If the timer is under a minute, a small button will appear:
Pressing the button adds another minute to the timer which gives you more time to join your server.
As soon as at least one player is on your server the timer vanishes and your server will stay online. After the last player has left your server the timer will come back and start to count down from the beginning.