Legacy Server : Unsupported Protocol/Cipher Mismatch

If you have a legacy server that does not have TLS1.2 enabled by default which will include Server 2008 though to Server 2012 and you get a client to talk to the server it will fail with error "The connection for this site is not secure" you will also get the text "unsupported protocol"

The reason for this is Chrome of your browser of choice is trying to talk TLS1.2 but that protocol is not enabled on the server, so the browser will fail to negotiate a cipher and protocol hence the browser will tell you "there is not certificate" installed as it cannot talk to to the server.

Note : When the client tries to talk the server if a common negotiation technique cannot be established then the connections fails, this is what has occurred in this scenario.

The problem needs to be fixed server side not client side, so from the server you need to ensure that KB3140245 is installed, you can get that from the update catalogue here this will allow the server is know about and support TLS1.2 and support it.

Then all you need to do is enable the relevant registry keys to get this working which will require a Powershell prompt (run elevated as an administrator) then you can paste the below into the shell:

New-Item 'HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2\Server' -Force | Out-Null

New-ItemProperty -path 'HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2\Server' -name 'Enabled' -value '1' -PropertyType 'DWord' -Force | Out-Null

New-ItemProperty -path 'HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2\Server' -name 'DisabledByDefault' -value 0 -PropertyType 'DWord' -Force | Out-Null 

New-Item 'HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2\Client' -Force | Out-Null 

New-ItemProperty -path 'HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2\Client' -name 'Enabled' -value '1' -PropertyType 'DWord' -Force | Out-Null  

New-ItemProperty -path 'HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2\Client' -name 'DisabledByDefault' -value 0 -PropertyType 'DWord' -Force | Out-Null

If you get no errors about no permission, then all you need to do is reboot the server and the next time you try that session from a Windows 10 or greater client you will now be able to use the website as you can see from below the communications is back online: