Hi. I just got an Arduino Uno and I tested it with an LED light and it worked. Now when I connect it to my computer, it doesn't work. The L light not blinking. The ON light instantly turns off. My computer can't recognize it. What it's wrong?
What "LED light"?
Red LEDs
sorry if my English is bad 
You mean a red LED?
If so, did you use a current limiting resistor between the LED and the Arduino? Did you disconnect the LED again?
Can you make a drawing how you connected things? Take a photo of the drawing and drop it here in a reply (try to limit the size to something reasonable like 300kB).
It fixed somehow. Now everything works
Ah, you pushed the USB right into the board then. This has been a common error we see every month or so!
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