Arduino Mega Uploading Problem

Hello everybody, a few days ago I borrowed my Arduino Mega board to a friend. Today I was working on a new project and found out that the board isn't being programmed. The Arduino IDE stays at "Uploading..." far too long and eventually gives some errors:

avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_getsync(): timeout communicating with programmer

I'm working on Windows 10. I have another Arduino Mega, a clone if that matters, which works fine and a Arduino nano that works fine as well. I tried to upload the Blink Example and it keeps giving errors.

Does anyone have any idea of what happened and how to fix the problem?

Thanks in advance,
José Coelho

Anyone facing the same problem?

Sounds like your friend has damaged the Arduino MEGA. Try the loopback test to see if the USB-to-Serial portion still works.

I tried the loopback test and it worked good.

If the loopback worked I guess it's time to watch the LEDs carefully and describe what they do when you try to do an upload.

The LED connected to pin 13 stays always ON, TX and RX never blink and the Power LED is always on. No LED blinks or changes state, they just stay always the same.