Why Does a Blank Screen Appear While the System Displays a Message Indicating Successful Authentication After I Attempted to Log In to an ECS Using VNC?

Another user has logged in to this ECS using VNC.

Only one user can log in to an ECS using VNC at a time. If multiple users attempt to log in to an ECS at the same time, only the first user can log in to it. For other users, the system displays a message indicating that the user is authenticated, but the screen turns blank. If this occurs, wait until the other user logs out of the ECS.