Dec 18, 2018 06:39 PM|yongcao99|LINK
Thank you @jzero. We found out that the 3rd-party is using TLS1.2 and our legacy ASP.NET 2.0 application is using SSL 3.0. The System.Net trace does not explicitly indicate that the protocols are mismatching.
TLS is enabled and SSL is disabled by default for Internet Explorer 11. That is why when entering the HTTPS URL in an Internet Explorer 11 browser, we can get a correct response from the 3rd-party web service. By disabling TLS and enabling
SSL, we got a "This page can't be displayed" message.
We need to upgrade our legacy web application to a higher version of .NET Framework to use TLS 1.2.