If your computer is not connected to the internet, several issues could be causing the problem. First, check your physical connections: ensure the Ethernet cable is securely plugged in, or if you’re using Wi-Fi, make sure the wireless switch is on and you're within range of your router.
Next, restart your modem and router by unplugging them for about 30 seconds and then plugging them back in. This can resolve many connectivity issues. Verify that your computer's network settings are correctly configured. On Windows, you can troubleshoot by running the Network Troubleshooter found in the Control Panel.
Check for any driver updates for your network adapter. An outdated or corrupt driver can cause connectivity problems. Also, ensure that no security software or firewall settings are blocking your internet access.
If the issue persists, contact your Internet Service Provider (ISP) to check for outages or specific settings that might need adjusting.