Upload s sketch to a 5v Pro-Micro board as 3.3V by mistake I have 2 types of Pro-Micro(as shown here), both 5v, micro-usb, which worked as expected, until, accidentally were flashed as 3.3v using the Arduino IDE.
At first I thought that the fact it stoped working right after, has nothing to do with that error, but since again, did the same mistake, I understand that this is no coincidence.
After doing so, boards seemed to be powered on ( leds are ON ), but are not found under port in the Arduino IDE.
Are they really can be destroyed by such an error ?
Holding RST and GND pins after re-connecting USB, showed it on port menu.
needed another such holding, prior to upload.
All good now.