I’m Er Tafseel Ahmad, an independent advisor, I’m happy to help you with this. . .
This is a very common problem with Windows 10 not expiring when buying a used PC, this error usually indicates a Windows 10 licensing issue and how to activate it. Most likely you have a volume licensed version of Windows 10 Pro installed. Not a consumer license. . .
Click on the start button, type cmd, then right-click on the command prompt and select’run as administrator’.
Run or paste this command and press Enter.
slmgr.vbs / dlv
Post a screenshot of the resulting dialog. . .