If your product/license key is not working, it may be expired. This means the validity of your product key has ended. If you activated Bitdefender a long time ago, the code will not work and the time will start from the day you made the payment on the Bitdefender Central account.
Hence, if your product key is not working, check whether you are putting in the right code and try to activate it. If you have recently bought the Bitdefender and are sure that the code is correct, please contact Bitdefender support.
Solution 2: Verify key validity