Here is a updates of the issue which I want to share with you first. According to the information you provided, the windows server 2012 client tried to connect to the WSUS server with proxy, but the proxy server is empty.
Reference picture:
Here is a updates of the issue which I want to share with you first. According to the information you provided, the windows server 2012 client tried to connect to the WSUS server with proxy, but the proxy server is empty.
Reference picture: