I have installed WSUS and configured it is supposed to be. Made sure that the port is accessible, the GPO has been updated in all machines, also I confirmed that the policy is was applied. But I still can't see the machines on the WSUS server. I have followed Microsft's manual: https://docs.microsoft.com/en-us/windows-server/administration/windows-server-update-services/deploy/2-configure-wsus#21-configure-network-connections
But even though no luck.