SharePoint Add-In - Exception occurred while trying to establish a connection with the remote server

Question

I have developed a SharePoint add-ins where I am retrieving information from a SQL server through an API that is hosted on Azure developed in asp.net web API. I am using "/_api/SP.WebProxy.invoke" method to get information from Web API. It has been working since last 3 years but now I am getting error as "An exception occurred while trying to establish a connection with the remote server - 'The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel" I checked Web API and it is working fine everywhere else, but not in SharePoint Hosted Add-In. We even checked SSL certificate and it is valid, not expired, and returns the correct response when accessed via Postman. Please help.

Answer 1

Hi @Pratibha Dawar , You can try to add following code to fix the issue

System.Net.ServicePointManager.Expect100Continue = false;