Hi,
Here are some troubleshooting steps that may help in resolving that issue.
- Start by uninstalling/reinstalling the Network adapter.
- Go to Device Manager and uninstall the Network adapter driver (Wired or Wireless)
- Reboot your PC once uninstalled and it should reinstall the driver automatically.
- Do try reconnecting once restarted and see if you can connect.
- If it won't connect still do try System Restore first, bring it back to an earlier date or time when it was working properly.
- If System Restore will not work try loading the PC into Safe Mode with Networking first and see if it will connect.
- And if all these will not work try contacting your ISP first and they can't solve the issue I would suggest to run a Factory Reset.