1
If Windows was pre-installed on your laptop, then, there should be an OEM licence stored on the motherboard, and if you install the same edition (Home, Home Single Language or Pro) that was previously installed, Windows should activate automatically.
Where did you purchase the laptop and was Windows pre-installed on the laptop?
2
Download the free ShowKeyPlus app from the Microsoft Store.
Please provide a screenshot of that app window and please hide your product key in the screenshot.