I’ve got a device that we’ve uploaded the firmware to and the Particle LED is breathing red.
I’ve consulted the chart over at: https://docs.particle.io/tutorials/device-os/led/photon/
and none of the described methods talk about a breathing red LED, only Blinking.
A P1 sitting on your own board I take it. Did this work before? If this is your first time checking out the board/P1, could it be your system LED is not hooked up correctly and you’re really looking at breathing green?