In order to keep an Aternos server running 24/7, you’ll need to ensure that you have a steady internet connection and enough resources (like memory and bandwidth) on the machine hosting the server. You may also need to configure your router and firewall settings to accept incoming connections to the server.
If the server already has a dependable internet connection and enough resources, but it still goes offline, it is likely due to the maximum player capacity being reached, or the maximum uptime limit being exceeded. In this case, you can try restarting the server or upgrading to a paid plan with Aternos. This will increase the maximum players capacity and uptime limit.
Make Aternos Server Live
Required links given below:
For more details, You can simply watch this video