1) Check the sign-in screen to make sure the user account and password are correct.
2) Check if the network interface is enabled properly in settings.
3) Be aware the guest account might not have access to the internet.
4) If necessary, use a different user account with the correct access.
5) Try restarting the device or router if the internet service is interrupted due to any unforeseen circumstances.
6) If methods are still not working, contact the internet service provider (ISP) for assistance.