Cannot join any aternos servers.

I've been having trouble joining aternos servers, yet I can perfectly connect to servers like Hypixel. Whenever I try to join them and they're open, it either says cannot connect to server, but if it does not say that and I can log onto the server, it gives me this message. (In attachments) Yes, I have the right IP, right version, so I'm completely clueless to why I cannot join.