Arm Mbed OS support forum

PyOCD deploy failed, deploying using mass storage device

Hallo ,
I’m working NuMaker-PFM-M2351_NS board … I can compile and flash the code on the board normally without problem but I can’t open the debug session ( I try to start but it take a lot of time without any response and I have to disconnect the board to close it )and I have pop up window says “PyOCD deploy failed, deploying using mass storage device…”
so How can I solve this Issue.


Debug is not supported for this target at the moment in pyOCD. Mbed Studio is falling back to “drag and drop” style programming to flash the board in your screenshot.


I am noticing this problem also on my STM32 Nucleo-144 Board. It has just started up today, and I am having trouble pinning it down.
It will try to find the log files to see what happened.