I used a Leonardo board as a keyboard, and I can’t flash it anymore.
I read flashing bootloader again may fix this, and I have Mega2560 so mixing these tutorials:
 Arduino Leonardo Bootloader Replacement - iFixit Repair Guide
 How to Use Arduino Mega 2560 As Arduino Isp : 3 Steps - Instructables
I flashed ArduinoISP from samples to Mega; and make this wiring:
Mega Leonardo ICSP
50 → MISO → 1
51 → MOSI → 4
52 → SCK → 3
53 → SS? → RESET
And the capacitator on MEGA between RESET and 5V
Now I set the board to Leonardo, select programmer “Arduino as ISP”; the board as Leonardo, but when I try to burn bootloader I receive:
avrdude: Yikes! Invalid device signature.
Double check connections and try again, or use -F to override this check
Did I miss the wiring?