After upgrade from Windows 7 Pro to Windows 10, I also got the What You Own Inventory error message "This application is configured for use on only one computer". Since I did this upgrade on a cloned hard disk (so I could go back to Windows 7) I purchased another license having What you Own Inventory on another disk. However, with the error message, I could not even get into the program. I e-mailed WYO support about the problem and got my activation code along with the following fix procedure in Windows 10 and "IT WORKS!": Here is the solution on Windows 10:
Uninstall all WYO versions.
Open C:\Users\Public\Ticket folder
Delete the following file: WhatYouOwn-Win.Ticket
Restart Windows 10.
Download and install WYO 4.20 from http/www.whatyouown.com/?page_id=137 (basically the page to purchase a copy of the program)
Use your serial number to activate.
I now have a functioning program again.