The console shows the server's screen as if a monitor and keyboard were plugged in. It works even when SSH does not - after a mistake in the network, firewall or SSH configuration.
Press Console in the server panel. A separate window opens with the server's screen; sign in as root with the root password.
The console's toolbar has:
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Each console connection is one-time and ends when you close the window. Black screen? Press Enter - the system may have blanked the display.