You people need to check the simpliest things first. Always unsure the basic service is running on your computer.

Start, settings, control panel, administrative tools, services

ensure DHCP client is running and also that your PC is pulling an IP besides APIPA (automatic private ip addressing ... 169.254.x.x)

If it's not getting an address and the service is running, then its the intermediary between you and your network. Check your card then and make sure it's enabled. Right click network place. Properties. Ensure that LAN is enabled and not turned off. I get calls on this shit all the time. If it's a laptop, you possibly hit a hotkey to disable your NIC.