Yea, its always better to check voltage across vcc and ground for each ESC individually to ensure they are getting power!
But first, you have to measure the voltage across the vcc and ground where the IPC is connecting to the motherboard.
Be sure to be in Voltage measurement mode with appropriate range selected on the multimeter.
Also, use the fused sockets on the multimeter!
I will, and then move up the chain step by step.
EDIT - Btw which LEDs are not lighting up? the ESC ones or Naza LED? or neither!
Neither. When I connect the battery, nothing happens. No lights, no sounds. So I guess it's: a) a problem with my board, b) no power comes to the board. I'll check that tonight.