I recently built a new VM with Windows Server 2016 and installed Exchange Server 2016. As part of hardening the server, I implemented our normal security header and cipher suite hardening steps. The Exchange Control Panel (ECP) appeared to function properly after these changes were implemented, but about a week later I found an issue where one of the less commonly used pages would not open. The page would not load the style sheets and you could not navigate to the page when using the FQDN from the local server. The page mostly worked when accessing it via https://localhost/ecp or from the FQDN outside the network.