You're world is from that April fool snapshot from Mojang. It creates world in a different way so that our system is not able to recognise it.
What is your username on Aternos?
Diliberto
Posts by ExodusViz
The Aternos forums are now deprecated
Learn more about this change here.
For help regarding Aternos, we recommend you to visit our support center.
-
-
The download world button is not appearing when on the worlds tab and yes there is a world there because the region folder is full as you can see in the attachments