Ran across a problem all of a sudden with Azure DevOps agents giving me an SSL connection error. This seemed to be only affecting Windows 2012 R2 servers.
AgentServer] System.Net.Http.HttpRequestException: The SSL connection could not be established, see inner exception.
You’ll have to make sure to enable or re-enable the following ciphers by going into the Cipher Suites in IIS Crypto. This works even if you use the “Best Practices” or “PCI 3.2” template.
Also, enabling the “Server Defaults” template works as well because it re-enables those ciphers.
I found some information about this issue here: Azure DevOps Agent installed on Windows Server 2012 R2 unable to TLS1.2 handshake with Azure Devops Agent Server https://developercommunity.visualstudio.com/t/azure-devops-agent-installed-on-windows-server-201/1651426
IIS Crypto can be found here: https://www.nartac.com/Products/IISCrypto