Sometimes the IP will be IPv6. JetPatch does not support this scenario. In order to account for this, you must disable IPV6 on the WSUS server (including any replicas).
To fix it, complete the following steps:
1) Disable IPV6 in the Network Adapter
2) Make the registry changes described in this article
3) Reboot the machine
Alternatively, you can run the task "Disable IPV6 Windows" from JetPatch.