Please make sure that your devices are in the same power loop. In addition, if any sort of extension cord, uninterruptible power system (UPS) or surge protector are present, these appliances may possess filter protective or surge protective features that will interfere the synchronization of your BiPAC 2071/2072/2073/2074. Thus, plug in your BiPAC 2071/2072/2073/2074 devices directly to the wall socket to avoid the interference.