[Solved] Firmware upgrade stuck  

Firmware upgrade stuck

I have just gotten my Prusa Original MK3S and try to upgrade the firmware with the latest.

First I had some trouble getting my Mac to communicate on the com port (when I hit the Flash button) but after some tries it began to upgrade.

After maybe 15 seconds (about 1/5 on the progressbar) the log says:

Writing | #################################avrdude-slic3r: stk500v2_recv(): timeout
avrdude-slic3r: stk500v2_recv(): timeout
avrdude-slic3r: stk500v2_getsync(): timeout communicating with programmer
avrdude-slic3r: stk500v2_command(): failed miserably to execute command 0x06
avrdude-slic3r: stk500v2_loadaddr(): failed to set load address
avrdude-slic3r: stk500v2_recv(): timeout
avrdude-slic3r: stk500v2_recv(): timeout

Now the display on the printer reads "Upgrading firmware Do not disconnect!" and a star moving back and forth.

It has been like that for about 15 minutes now. How long should it take?

Any suggestions on how to proceed?