Means a break or short in the circuit. Usually happens when a bulb has blown. Are they all flashing? Check fuses.
I would check that the two live wires to your brake lever are connected as GN says. They are hard to spot, two tiny black wires on spade connections to the underside of the throttle housing. Failing that, check the two (blue?)live connections to the horn above your front mudguard. They take a lot of abuse being so exposed to the weather, and your front brake light circuit takes its live from there. Have you had the front fairings off? If so check the barrel connections between the bike and the indicator mounts have been pushed home properly. If you have a multimeter, you could check that the switch at the lever is functioning correctly.