where is problem, UNO cannot be uploaded and communicated?

Hello, Yesterday I used the UNO and motor shield to drive a stepper motor, but the current is too high which leads to be hot of the plate.

But it works of driving the motor.

Today I also to start the motor, but it does not work. I have tested Motor shield, It is not broken.

And my computer cannot detect the UNO plate, usually what is problem? Is it burned ?