Arduino not responding to macbook pro

Question

When I try to upload my code onto the Arduino it just gives me the error message: "avrdude: ser_open(): can't open device "/dev/cu.usbmodem14201": No such file or directory Problem uploading to board. See http://www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions."

My Arduino used to function just fine. Now when a plug it in, the lights on the Arduino do not blink like they used to, and the only pins that do anything are the ones to power. It also said something like: Arduino is not optimized for mac os. It seems that the Arduino is taking in the power but not the code. here's the code:

int led = 13; // the pin the LED is connected to
void setup() {
  pinMode(led, OUTPUT); // Declare the LED as an output
}

void loop() {
  digitalWrite(led, HIGH); // Turn the LED on
}

Answer 1

I had this issue and it was because the port was not set in my Arduino IDE.

I fixed it by going to Tools -> Port, and selecting my usb device. In my case it was called /dev/cu.SLAB_USBtoUART

Answer 2

I fixed it by plugging it into my other USB port (which I had previously been using)

So possibly this is caused by switching USB ports