In order to troubleshoot this issue, please follow these steps:
1. Click the icon at the top of the Bitdefender's main interface and select Account Info from the drop-down menu.
2. Click on the Switch Account button.
3. Type the e-mail address and the password of your Bitdefender Central account in the corresponding fields, then click Sign in.
NOTE: It can take up to a few hours for your device to show up in Bitdefender Central.