It is highly unlikely that both BeoLab speakers have faulted at the same time with the same fault. The first thing to check is the powerlink cable (the thin cable that connects the audio to the speakers).
Have you had a carpet laid?
Is it possible that the cable has been damaged?
Do you have any pets that could have chewed the cable?
Alternatively it could be the audio unit itself. Without other equipment it is difficult to fault find. If you have access to another pair of active speakers, you could see if they work with your cables.
Hope that helps
Opman