The modem's lights are a visual indication of its current status. It is normal for your US/DS (upstream/downstream) lights to flash briefly while establishing a connection. Continuously flashing or blinking US/DS lights indicate that the modem is unable to establish a connection due to poor or no signal.
Typical reasons for this are:
There is a service outage.
There is a wiring misconfiguration.
The modem is defective.
If you are experiencing this condition, first check for a service interruption by: