Hi Althaf,
Welcome to Microsoft Q&A platform.
I’m really sorry you’re dealing with losing access to your brand-new product key.
In case you bought the product from a third-party seller or online marketplace, it’s worth contacting them directly to report the issue and ask about a refund or replacement.
Otherwise, you need to reach out to Microsoft Support immediately, make sure you have your purchasing proof of to help verify your ownership.
You can contact them here: https://support.microsoft.com/contactus. They’re best equipped to investigate this issue and help you figure out what happened.
Let me know if you need further assistance, I’m willing to help.