Rocket Lab Electron 2nd Stage Failed - Loss of Payload
(twitter.com)https://twitter.com/RocketLab/status/1393531340188913665From the live stream, it appears that the 2nd stage motor started, then stopped a couple of seconds later. If so, I'm guessing a sudden loss of power to the electric propellant pumps.
ETA: Appears to have spun hard shortly after staging.