An update was released recently (9/25) that addressed some players' ability to connect to games on Steam. Please restart Steam for the update.
If you continue to experience Steam connectivity issues, please try the following:
Borderlands 2 uses Steamworks, so we recommend following their troubleshooting steps here to identify and resolve any networking issues: https://support.steampowered.com/kb_article.php?ref=1456-EUDN-2493
If following the steps in the above doesn't resolve your issue, please submit a ticket to us with the following details:
- Have you disabled any software firewalls that may be preventing other players from joining?
- Is your anti-virus or other programs rejecting connections?
- Are you on one of the networks that has Steam issues https://support.steampowered.com/kb_article.php?ref=1456-EUDN-2493#isp
- Can you connect to others through invites/player list?
- Can other connect to you through invites/player lists?
- Can players connect to you when you are hosting a public game?
- Can you connect to other players through quick match or match browser?
- What is the name of your internet service provider?
- What is the manufacturer and model number of your modem?
- Is your modem plugged into a router? If so, what's the manufacturer and model number of that router?