My assumption is that the error message regarding "not having the correct login or something" is probably the one telling you that you haven't added a Game Server Login Token (GSLT) from Steam to your server yet, whoch is why it isn't appearing in the Steam server list.

Refer to official documentation for server hosting: https://github.com/SmartlyDressedGames/U3-Docs/blob/master/ServerHosting.md

For generating a GSLT specifically, see: ...

Sorry that it took me a while to respond to you again! I was looking through some other errors & work. I wrote up some potential issues / fixes that I was going to send you, but since you've fixed the problem it seems a bit moot now.

I'm glad that you were able to fix the issue on your own though!

I'll leave a shorter version of my suggestions below. Although you don't need them anymore, you might still find them helpful. Or maybe someone else will a similar issue come across them:

What I was originally going to say:

I took a closer look at the images you posted. Here's my current thoughts on potential issues:

• Unity 2018.4.36f1 is very outdated. You'll need to either update Unity or adjust your MasterBundle.dat file.
• Make sure you've tagged your main folder with an asset label.
• Double-check that your MasterBundle.dat is correct.

You can use older Unity versions, but it's better to use the same...

For masterbundles, it's important that you tag your folders (and only the necessary folders) correctly. Additionally, your file path in Unity should be 1:1 with your file path in-game.

You most likely didn't bundle your mod correctly. Providing more information or images from Unity would likely be helpful.

I'm glad that you were ultimately able to resolve this issue on your own. I hope you and your friend were still able to have a fun time in spite of the problem.

The reason the error is fairly vague is because the game just cannot know where along the line the connection failed – just that it did (because the connection was never established). Note that the server info you see before joining is just from the Steam server list; you don't actually attempt to connect to the server until you actually click the button to join.

With that being said: it'd make sense to update the support article to provide more information regarding host-specific issues (e.g., how in this case it was a port forwarding issue). I'll make a note that the article should be tweaked further.

Thank you for sharing.

Unfortunately, because this is a vague error that typically isn't caused by the game itself, I can't provide step-by-step instructions to fix it. It'd be easier to narrow down the actual issue first.

The linked support article gives advice on narrowing down the cause of the issue, which would make it easier to resolve (or if it's caused by something like your AV blocking it, then you would resolve it by creating a exception as mentioned in the support article).

If OP (or someone else) is unable to resolve the issue with just the relevant articles, they can file a support ticket from the website as well.

Good luck with your map development project!

Players cannot build in the main city of Elver. Try building somewhere else.