Having trouble connecting to friend's server's while on my Mac

io.netty.channel.ConnectTimeoutException: connection timed out

This is the message I get with every single attempt I make to join one of my friends servers, and I don't know why this keeps happening.

I've gotten the ip down correctly, and I'm running the current version of the game like my friend is.

I can still connect to other servers just fine, but if they have Aternos in the name it times me out.

Is there anything I need to modify in my security preferences at all?

Mind you, this is my first attempt at using terns servers at all, so this is all greek to me. apologies for my unawareness

Current version of the game is 1.17.1, and my software is Java.

I'm unfamiliar with the DynIP however, could you perhaps explain that to me?