J'ai eu le même problème quand j'ai voulu flasher le bootloader sur ma CR10.
J'ai utilisé la méthode alternative décrite là : https://www.instructables.com/id/Flashing-a-Bootloader-to-the-CR-10/ et tout est rentré dans l'ordre.
Je cite : "
IF EVERYTHING DID NOT WORK CORRECTLY, THERE IS AN ALTERNATIVE METHOD THAT YOU CAN USE!
So you're sure you did everything right and you tried to burn bootloader yet it didn't work? Here is an Alternative Method using a sketch made by a brilliant man named Nick Gammon.
Download Nick Gammon's sketches from here. (Nick Gammon's web page can be found here)
Extract the zip somewhere. Documents\Arduino is a good place.
Back in the Arduino IDE, click File > Open
Find the folder you extracted Gammon's sketches to. Inside that folder, there will be a folder named Atmega_Board_Programmer and inside that folder, a file named Atmega_Board_Programmer.ino. Select that file and open it.
Now set your board (Tools > Board) to the Arduino UNO and your port (Tools > Port) to the com port of the Arduino UNO, and your programmer (Tools > Programmer) to the AVRISP mkII
Upload the sketch.
Wire everything up as previously stated in this guide and connect both boards via USB to your PC.
With everything still set up for your Arduino (Board, Port and Programmer), in the Arduino IDE, select Tools > Serial Monitor.
Inside the Serial Monitor window, there are two drop down boxes at the bottom right, set the first to "Both NL & CR" and the second to "1152000 baud".
Some text should scroll by. If you get a message saying "Failed to enter ICSP programming mode" something is wired incorrectly.
If you get the message "Type 'Q' to quit, 'V' to verify, or 'G' to program the chip with the bootloader ...", type G in the text box at the top of the window and click the send button.
If preformed correctly, it will flash the bootloader."