Downstream WSUS server in a single domain has not been synchronizing.

Downstream WSUS server in a single domain has not been synchronizing. Tried reboot, then manual synchronization and get a failure with the following detail information within 30 seconds. Was working fine a month ago.

An HTTP error occurred:

WebException: The underlying connection was closed: An unexpected error occurred on a send. ---> System.IO.IOException: The handshake failed due to an unexpected packet format.
at System.Web.Services.Protocols.WebClientProtocol.GetWebResponse(WebRequest request)
at System.Web.Services.Protocols.HttpWebClientProtocol.GetWebResponse(WebRequest request)
at Microsoft.UpdateServices.ServerSync.ServerSyncCompressionProxy.GetWebResponse(WebRequest webRequest)
at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters)
at Microsoft.UpdateServices.ServerSyncWebServices.ServerSync.ServerSyncProxy.GetAuthConfig()
at Microsoft.UpdateServices.ServerSync.ServerSyncLib.InternetGetServerAuthConfig(ServerSyncProxy proxy, WebServiceCommunicationHelper webServiceHelper)
at Microsoft.UpdateServices.ServerSync.ServerSyncLib.Authenticate(AuthorizationManager authorizationManager, Boolean checkExpiration, ServerSyncProxy proxy, Cookie cookie, WebServiceCommunicationHelper webServiceHelper)
at Microsoft.UpdateServices.ServerSync.CatalogSyncAgentCore.SyncConfigUpdatesFromUSS()
at Microsoft.UpdateServices.Serve