I’m having this same issue. I have a release Photon that I got a few days ago, and I am unable to flash any new code. Everything works exactly like it should with no error messages, but the code does not run. I can still use Tinker. I’ve done multiple factory resets and upgraded the firmware via DFU (using the comand above) multiple times.
When I flash I get the standard magenta, then flashing green and then breathing cyan. The only clue I have is that doing a system reset or wifi reset doesn’t actually erase the wifi settings. It is always able to reconnect to my WIFI immediately after a factory or wifi reset. Any ideas?