We would run into this issue while trying to connect to Dynamics 365 Version 9.0 from a client application.
It is because Customer Engagement Platform (version 9.0) only supports TLS 1.2.
More details here
How we can fix it à
We need to add the following line of code to our existing code
public static OrganizationServiceProxy GetOrganizationServiceProxy() { ClientCredentials clientCredentials = new ClientCredentials(); clientCredentials.UserName.UserName = "username"; clientCredentials.UserName.Password = "password"; // Set security protocol to TLS 1.2 for version 9.0 of Customer Engagement Platform ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12; return new OrganizationServiceProxy(new Uri("https://orgname.crm.dynamics.com/XRMServices/2011/Organization.svc"), null, clientCredentials, null); }
Helpful post
Hope it helps..
Reblogged this on Arun Potti's MS CRM blog.
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