Hello @cmcrrr
you might want to force M5StickCPlus2 into download mode manually. Below are the steps:
disconnect USB press and hold PWR button until green LED lights up, then release button connect a wire from G0 to GND attach USB press and hold PWR button until green LED lights up, then release button remove wire--> M5StickCPlus2 is now in download mode. Use M5Burner to erase or flash something.
Thanks
Felix