Windows 10: can't register my laptop in ms account

I have a YOGA laptop I purchased new from Bestbuy. I have never been able to register it as a device. When I try to register, the registration form states that the serial number is not recognized. OTHER 2 computers registered just fine some time ago.

:)

 

register PC with microsoft; use local account to log in

I bought a used laptop running Win 10 Pro. winver reports 1809.
How do I register my PC with my Microsoft account?
But when I'm done, I'd like to use my local account each time to log in.
Please tell me how to do that.
I am very new at Win 10, and need step by step instructions.

Thanks,

 

Remove account

I suggest you backup your personalized files first before removing the account.
To delete an account, follow these steps:

1. Press WIN + X keys and click Command Prompt (Admin) from the menu.
2. Type the following command and press Enter. Replace test with the name of your sister's account. Code:

 

register PC with microsoft; use local account to log in

Just simply log in with your Microsoft Account.
Switch to Microsoft Account in Windows 10

Just go back to using a local account:
Switch to Local Account in Windows 10

Hopefully the tutorials are step by step enough.