Hi, Thank you for the tip. It worked for us. We've experienced the same problem after trying multiple times on different computers.  We have 6 user licenses and all workstations are up-to-date for the QB Enterprise ver. 23.  After I logged off the Intuit User account on the top right hand corner, QB let me switch to Single User mode.  

On a separate note, you can stay in multi-user mode to import a iif file of payroll time.  You just need to be logged in as Admin.