Thank you for your answer. I did the connections from Rx/Tx and RESET to GND and nothing changes. The pc not recognize it when I connect it to USB (it was COM3)... my Arduino UNO works perfect with the same cable and same USB port (and all the time they worked in this USB port).
I was working with I2C communication between them with power supplies separated... I don't remember something suspicious.
I think ICSP is my only chance,( but I don't know what I need). Thank you and regards

Hello, I did this procedure with my Arduino Mega board and nothing different happens. The problem is no usb communication and the two leds RX and TX still on (half power). Here is a little video to show you. Thank very much