In IIS 7.5, which is installed on Windows 2008 R2 servers, only SSL 3.0 and TLS 1.0 are enabled for HTTPS encryption by default. To enable TLS 1.1 and TLS 1.2 and disable the insecure SSL 3.0 protocol, add the following keys to the Registry of the server:
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\SSL 3.0\Server]
"Enabled"=dword:00000000
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.0\Server]
"DisabledByDefault"=dword:00000000
"Enabled"=dword:ffffffff
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.1\Server]
"DisabledByDefault"=dword:00000000
"Enabled"=dword:ffffffff
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2\Server]
"DisabledByDefault"=dword:00000000
"Enabled"=dword:ffffffff
After a reboot, IIS should be accepting TLS 1.2 connections.
From: https://basics.net/2015/10/06/iis-7-5-how-to-enable-tls-1-1-and-tls-1-2/