Hello, Welcome to Micorosoft Q&A,
Your issue that might be related to VPN proxy network and I'm afraid is not suitable to discuss in the Forum. For your scenario, I suggest that you might need to open a support ticket for this. Please contact our paid phone support at MS Support. You will get 1:1 support on that. Select Developer Tools -> Windows UWP Development -> Windows 10 Universal App Dev -> System Services Development-> Networking API in the support page and you could contact the team. Please kindly note that your support ticket will be free if it is Microsoft's issue.
If the response is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.