Access your BullGuard account from here and login with your username and password.
Scroll down to the Active Installations section which should look like this:
From this list you can Enable or Disable the BullGuard installations you need by clicking the Enable/Disable slider (the green slider highlighted in the above screenshot). Each entry in the list shows the Device Name of the computer on which that installation of BullGuard was last recorded.
To find the Computer Name right-click on Computer and select Properties (for Windows Vista, 7) or right-click on the Windows button and choose System (Windows 8, 10). In the window that opens you should be able to locate the Computer / PC Name.
Finally try to re-login with your BullGuard username (email address) and password inside the BullGuard program on the computer which needs to have the BullGuard installation active.