you could follow this tutorial , then learn how to setup the usb mode
@stuartt erase flash , then reburn the uiflow firmware
1 . long press the power button, when the log show "Connecting.................._____."
seting the upload speed to 115200
connecting GND to G0 , when you upload program.
could you erase the flash? then burn the firmware again?
If none of the above works, please contact our store ， thanks