There are a number of possible culprits...
- bad server configuration
- firewall blocking access to ports
- router/port forwarding config issues
Unfortunately, without you having some knowledge on how to debug these issues, you're not going to get far... We can't figure it out on this end, we can only guess and cross our fingers. If you don't know how your home network is laid out, and can't configure it yourself, any advice I give is likely to sound like gibberish.
ie, to check your port forwarding settings, you need to login to your router (or perhaps modem, if your modem has one built-in) using the username and password you set up when you installed your network. Then find the port forwarding properties page, (varies by manufacturer and model) and make sure that the dedicated server's port (27015 by default) is forwarded to the IP address of the computer running the dedicated server.
Did any of that make sense?
