I have not read the whole thread again, so things I’m saying might have been said and tried already.
Still, to reiterate, you might need to remove any previously installed Particle Serial USB drivers.
This can be tricky since Windows - by default - won’t show you drivers not currently in use.
To get around this, try following this procedure (shown for XP, but still applies to 10)
https://support.microsoft.com/en-us/kb/315539
When you’ve done that, you should now see Particle drivers (if you ever had them installed) and can remove them and any other drivers which might have been used for the Photon.
Make sure to tick the “Remove from system” checkbox in order to get rid of them completely.
After that reboot the system, then open DevMgr again to see if there are any remainders and see where a newly plugged-in Photon will appear.
It should come up as COM port. If it doesn’t you can try zadig - which you should have or will need for DFU driver install anyway - to force feed Windows the USB Serial (CRC) drivers.
After that you should be good to go.