In our series 'you are never to old to learn' : this saved me after an hour of frustrations with different cables and OS's Should have known better after all my ESP adventures. Here it is for future use: if your #prusa does not want to flash with this error: "avrdude-slic3r: stk500v2_getsync(): timeout communicating with programmer", then do this: press reset on the printer and immediately after start flashing. Source: https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-hardware-firmware-and-software-help/having-trouble-updating-to-the-latest-firmware/#post-162457