Hi paeyongC-
I'm Kevin B. Windows user like you. I do apologize for the inconvenience, let me help you sort things out.
Does your Windows came pre installed or you get it separately before?
How did you perform reset? Is it just on the settings or you perform using boot device?
Kindly press Windows key and search for command prompt.
Right click on it then run it as administrator.
Type: slmgr.vbs /dlv
Hit enter.
On the resulting dialogue, take a screenshot and post it on your next comment.
Kindly take a screenshot of your activation section on your settings as well and hide some personal information on it.
I await news. Have a blessed day!
Thanks,
Kevin B.
Independent Advisor