The Excel Addin uses the dotnet 4.0 framework that defaults you to TLS 1.0 communication protocol.

This now out-of-support protocol version is incompatible with some server upgrades or enterprise network infrastructures.


To force the Execl Addin to use TLS 1.2 protocol you need to apply three registry keys (script attached).


[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework\v4.0.30319]
"SchUseStrongCrypto"=dword:00000001

[HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Microsoft\.NETFramework\v4.0.30319]
"SchUseStrongCrypto"=dword:00000001

[HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Microsoft\.NETFramework\v4.5.25000]
"SchUseStrongCrypto"=dword:00000001