With a new P2 on a custom board - previous revision of board worked fine and no changes made to USB connection. This latest revision if I use setup.particle.io on Chrome then No compatible devices are found. Any idea other than the micro USB socket is not connected to the P2 (PCB issue)?
It's usually the soldering on the USB connector.
On Windows you can check the Device Manager, on Linux lsusb, and on Mac ioreg -p IOUSB to see if the operating system can see the device.
Actually the most common reason is a power-only USB cable, but presumably you checked that.
@rickkas7 Thanks for the suggestions. Not the cable - as that works for the old board. I am going to try the electrical conductivity from USB D+/- and P2 pins but that's not easy!