Hi VPSA
Unfortunately, once a Windows Server has been reinstalled, the product key cannot be retrieved directly from the system. Since you have documentation proving your purchase, the next step is to contact Microsoft Support for Business or your reseller/OEM partner who issued the license. They can validate your proof of purchase and reissue the product key or provide guidance on recovering your entitlement. If the license was purchased through Volume Licensing, you can also log in to the Volume Licensing Service Center (VLSC) to download the key.
I recommend opening a support case via support.microsoft.com and attaching your purchase documentation so the team can assist you promptly.
I hope this helps 🙂. If you find this answer useful, please click “Accept Answer” so others can benefit from the guidance as well.
Harry.