If players are not able to join your game, you may have a firewall in place. Firewalls may prevent incoming networks from reaching your computer and prevent you from hosting games or joining games.
Check out the information provided and give these a try before creating a new topic!
Ports & Firewall Information
If you did not change your networking equipment and you suddenly are not able to host, your internal IP address may have changed. Check your router’s Port Forward section and make sure it is still forwarding information to the right computer.
If these resources do not help, please try the steps on our Connection Troubleshooting article.