How to recover bit defender activation key

Hello @Santanu_100 and welcome to the Community!

If you have an ongoing subscription with Bitdefender, you can install protection on the Windows 10 device directly from the Central account. The activation code is no longer needed in the installation process. As you have reinstalled your operating system, the first step would be to access the Bitdefender Central account and remove the device from there, to free up the slot. This is necessary because Central will still display the device there, although it will no longer be protected, because Bitdefender was removed from it. Then reinstall protection on that device and once the installation process is complete, the device will be displayed as protected, both in Central and in product. Below you will find the steps required:

Let us know how it goes.

Best regards.