Problem with Arduino MEGA ADK

Hello everyone.

I'm having some trouble with my Arduino Mega ADK for Android.

It is not recognized by USB when I connect. The green LED is on and the orange LED blinks when I connect or press the reset button, but my PC do not detect it. I'm using Ubuntu 16.04 LTS but I tried on my other computer which has Windows 8.1 installed and it didn't detected it too. I also tried on a MAC and had the same problem. The Tools->Port option is grayed at the Arduino IDE. Two days ago I used it and it was working normally.

When I access the /dev directory there is no ttyACM0. The lsusb command result is:

Bus 002 Device 002: ID 5986:0145 Acer, Inc
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 008 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub

When I try to upload the code, the IDE shows the following message:

Arduino: 1.8.4 (Linux), Board: "Arduino Mega ADK"

Sketch uses 1462 bytes (0%) of program storage space. Maximum is 253952 bytes.
Global variables use 9 bytes (0%) of dynamic memory, leaving 8183 bytes for local variables. Maximum is 8192 bytes.
avrdude: ser_open(): can't open device "/dev/ttyACM0": No such file or directory
ioctl("TIOCMGET"): Inappropriate ioctl for device
ioctl("TIOCMGET"): Inappropriate ioctl for device
avrdude: ser_send(): write error: Bad file descriptor
avrdude: stk500_send(): failed to send command to serial port
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: ser_send(): write error: Bad file descriptor
avrdude: stk500_send(): failed to send command to serial port
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: ser_send(): write error: Bad file descriptor
avrdude: stk500_send(): failed to send command to serial port
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: ser_send(): write error: Bad file descriptor
avrdude: stk500_send(): failed to send command to serial port
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: ser_send(): write error: Bad file descriptor
avrdude: stk500_send(): failed to send command to serial port
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: ser_send(): write error: Bad file descriptor
avrdude: stk500_send(): failed to send command to serial port
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_getsync(): timeout communicating with programmer
the selected serial port avrdude: stk500v2_ReceiveMessage(): timeout
 does not exist or your board is not connected

This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.

I've already used the commands

$ sudo usermod -a -G tty myUser
$ sudo usermod -a -G dialout myUser

But it didn't work.

I'm starting to think it's a hardware problem.

Can anybody help me please?

Thanks