Can't join my friends' Aternos server

Hello. I've been trying to join my friends' Aternos-server for a few days, and every time I join I get this error message:

board.aternos.org/wcf/attachment/4731/

I've tried using the aternos-IP and Dyn-IP (in both number and text form).

I'm running the same version of Minecraft as my friends and the server (1.17.1).

I can join other aternos servers just fine.

Here's the log after I tried joining twice. As you can see, the server doesn't even detect me trying to connect.

This is the error message that is displayed when I try to join the server.

That's weird, on my end it displays a screenshot of the error message.

In plaintext form the error message I get is this:

io.netty.channel.AbstractChannel$AnnotatedConnectException: Connection timed out: no further information

I have flushed my dns, restarted my computer multiple times and reinstalled Minecraft. I have also allowed Minecraft Launcher through my firewall.

I can see the server in my multiplayer browser whenever the server is stopped, but after it gets started it disappears completely only from me. I get "Can't connect to server" even though the server is online and my friends are playing on it.

No, as I noted in my starting post.

I have tried the IP and the Dyn IP. Neither work. When the server is offline, I can see the "This server is offline"-message. As soon as the server is starting and goes online it just gives me "Can't connect to server".

In addition, I can join my own aternos server as well as other servers just fine.