Ok so
- Your computer + Linux: works
- Your computer + Windows: ?
- colleague’s computer + Windows: fails
- colleague’s computer + Linux: fails
Is that right?
I can suggest a few things:
- manually put the target board into bootloader mode by conncting GPIO0 to GND and issuing a reset (either power on-off-on or briefly connect EN pin to GND). Does it always upload then? If yes, there is an issue with the USB-serial converter drivers or the timing of the reset signal
- there are tricky gotcha’s as e.g. explained in https://www.youtube.com/watch?v=roMjPoaFAZ8
- there may be driver problems, for Windows 11 it is e.g. known that only a particular version / type of Silabs CP210x driver works: Windows 11 problem with connecting to ESP32 (ESPTOOL-374) · Issue #706 · espressif/esptool · GitHub. This driver is also valid for Windows 10.