If your friend has a server and you can’t get it to show up on your list, then this guide might be able to help you. Also, this issue is a bit finicky, so there’s a chance that this may not work for you.
TL;DR:
- Open Steam window.
- Go to View and then down to Servers.
- Go to Add Server.
- Type in the IP and the port, then add the server.
- Refresh and QUICKLY right click on the server.
- IF you can join game, do so.
- You may have to try refreshing a few times.
- You may also need to check the IP address and port number.
- Try adjusting the port up or down by one.
- Enter any passwords that are needed and you should be good.