Incompatible or no bootloader present! Please burn correct bootloader

[stoutouloutou]

Hello,
First of all, thank you for the work done, and sorry if I'm missing an obvious mistake, I took some times searching around but didn't find an answer, before posting this message.

Well, I have a chinese copy of Arduino ATMEGA 2560, and try to use optiboot for the OTA update capability.

The flashing of the bootloader seems to go well (using arduino IDE and usbasp, MCUdude/MegaCore), but when I then upload and run the serial_read_write example, I get "Incompatible or no bootloader present! Please burn correct bootloader" on the serial monitor...

Here are the logs of the bootloder flash :
bootuploadlog.txt

Am I missing something ?

Thanks for your help !