First, the basics:

• Check cables: Ensure Ethernet cables are secure. For Wi-Fi, confirm your device is within range and the network isn't hidden.
• Restart everything: Give your computer, router, and modem a quick reboot. This often magically fixes glitches!
• Run diagnostics:Windows has a built-in network troubleshooter, accessible through Settings. Use it to diagnose and potentially fix the issue.

If that fails:

• Forget and reconnect: On Windows, forget your Wi-Fi network and re-enter the password. This refreshes the connection.
• Check airplane mode: Ensure it's disabled, as it can block internet access.
• Driver update: Outdated network adapter drivers can cause problems. Update them through Windows Device Manager.
• DNS settings: Try setting your DNS servers to Google's public DNS (8.8.8.8 and 8.8.4.4) to rule out DNS issues.

Advanced options:

• Network reset: Windows has a network reset option that reverts settings to defaults. Use it as a last resort.
• Contact your ISP: If nothing works, your internet service provider may be having issues. Contact them to check.

Remember, the specific steps might differ depending on your operating system and hardware. Google your issue for detailed instructions tailored to your situation