Hello, @Loonsong55. Thank you for joining the Community where your needs met with great people.
What's happening is when switching to Single User Mode, it is stating someone else logged on, and we call this a Ghost User. It can occur if sometimes you don't log out of your desktop application at least once or twice a month.
To stop this error from occurring, you can log out of all devices and then shut down all computers and host and leave it off for at least one minute. Bring all computers back up and try logging back in again.
It will take away the Ghost User and allow you to switch to Single User Mode.
Please, if you have any more questions or concerns, don't hesitate to reach back out. Happy Friday!
