Hello! I am really new to Arduino and I put leds in the slots 12 and 13 which i want to control with my programm which should let them blink. First 13 than 12 and so on. Everything works just fine, but the pin number 12 doesnt work because the led doesnt blink. My code is correct by the way.
is your 'failed' LED the right way around?
Have you tried swapping the LEDs to see if one of them is faulty?
Do you have resistors in line with your LEDs?
Could you post your code please?