TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 in windows server 2012 r2

Unfortunately Windows 2012 Server doesn't support tls-ecdhe-rsa-with-aes-256-gcm-sha384 or 256/128 Ciphers.

Microsoft has a docs page that lists all the Windows versions and their cipher suites.

First server version to support this cipher suite is indeed Windows Server 2016.