1
You may not need to product key to reactivate Windows, it depends on where you purchased your Windows licence did you purchase the Pro licence directly from Microsoft, and if so, is that a full retail Pro licence or a half-price Home to Pro upgrade licence, or did you purchase the Pro licence form a 3rd party retailer?
2
Log into your Microsoft account online in a web browser, go to the Devices section, do you see the currently activated device listed on your account.
3
Download the free ShowKeyPlus app from the Microsoft Store.
Please provide a screenshot of that app window.
This is a public user forum, please hide any product key in the screenshot.