Nest Cam with Floodlight, floodlights constantly flashing

[G-Bomb]

I've just installed the Nest Cam with Floodlight, but when I switch power on to it, the floodlights just flash, the indicator lamp pulses white then turns off and it never goes into pairing mode.

I've checked the power running to it and that's fine, constant.

I've tried a factory reset and again, no change.

[G-Bomb]

I just wired the camera to a three pin plug and plugged it in and it worked just fine, but I then wired it back into my upstairs lighting circuit and it just flashes again!

[MplsCustomer]

@G-Bomb 

We don't have the floodlight camera, but perhaps it requires being connected to a grounding wire.