Check the Electronics to make sure ABS is not turned off... if that is possible on a 959.
Then check the ABS sensor and ring on the wheel that had the tire changed
Check that they have put the wheel back on the bike with the ABS ring on the same side as the sensor. It has happened that the wheel has been reinstalled the wrong way around so the ring is on the wrong side, then the ABS light comes on until the wheel is flipped