Website Error - ERR_HTTP2_INADEQUATE_TRANSPORT_SECURITY.

When loading any website you get the error - ERR_HTTP2_INADEQUATE_TRANSPORT_SECURITY

This is due to security setup on your 2016 windows server host, typically adopted for security of weaker ciphers.

Resolution. 

Currently the best way to deal with this is to disable http2 and use http1.1 by default.

To do so set the following registry value on the Windows deployment of IIS or your machine the error occurs on:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\HTTP\Parameters

EnableHttp2Tls REG_DWORD 0

EnableHttp2Cleartext REG_DWORD 0

The second of these is only necessary if the failure is with HTTP. The first is for HTTPS, we would suggest using both. If you plan on re-enabling security http2 you can either delete the keys or set the value to 1.

Once set, the machine MUST be restarted.