The request was aborted: Could not create SSL/TLS secure channel

Question

We are unable to connect to an HTTPS server using WebRequest because of this error message:

The request was aborted: Could not create SSL/TLS secur

Answer 1

This question can have many answers since it's about a generic error message. We ran into this issue on some of our servers, but not our development machines. After pulling out most of our hair, we found it was a Microsoft bug.

https://support.microsoft.com/en-us/help/4458166/applications-that-rely-on-tls-1-2-strong-encryption-experience-connect

Essentially, MS assumes you want weaker encryption, but the OS is patched to only allow TLS 1.2, so you receive the dreaded "The request was aborted: Could not create SSL/TLS secure channel."

There are three fixes.

1) Patch the OS with the proper update: http://www.catalog.update.microsoft.com/Search.aspx?q=kb4458166

2) Add a setting to your app.config/web.config file.

3) Add a registry setting that was already mentioned in another answer.

All of these are mentioned in the knowledge base article I posted.