By default, the Windows .net Player uses the standard crypto libraries provided by the Microsoft .net Framework.
If you need to use a CMS that provides only TLS 1.2 connections, then you will need to ensure you set the following registry settings:
32 bit machines
Key: HKLM\SOFTWARE\Microsoft\.NetFramework\v4.0.30319\SchUseStrongCrypto
Type: DWORD
Value: 1
64 bit machines
Key: HKLM\SOFTWARE\Wow6432Node\Microsoft\.NetFramework\v4.0.30319\SchUseStrongCrypto
Type: DWORD
Value: 1
Original post that describes this can be found here - with thanks to @Jeremy_Sippel: