I haven't found any threads with an issue like this mostly display issues or compatibility mode problems.
ESXi6 build 41922238, Server 2008 R2
When I open the console from the vSphere Client (non Web Client), I get the normal ctrl+alt+del screen and when I enter that keypress it doesn't give me the login box its just blank (see attached image) not sure whats causing this I have no other methods to get into the server, RDP is disabled, powershell is also disabled for remote access.