Connection and password issue

Before I get started - If this is in the wrong place, I do apologize.
Trying to navigate the forum can be confusing to me. That said, I’ll begin.

I’m having an issue with running the clientside of a gmod session.
Some people can connect without entering a password, while others can’t, and end up getting a “Bad Password”
message, despite never getting the chance to enter a password.

Now this problem doesn’t happen via a dedicated server. They get the chance to enter a password, and can connect perfectly.
All the ports are forwarded correctly, the config info for the clientside is in the correct file (listenserver.cfg), and the
dedicated server info was correct as well (server.cfg). I’ve gone through the idiot test 3 times already, and I can’t figure
out what I’m doing wrong.

Any ideas?

Edit: I can’t manage or afford a dedicated server - this is simply for sandbox play.

Forget it. I’m not going to bother with Garry’s mod servers.