Can't print to Serial Monitor....

Serial.println is no longer printing to the serial monitor. I am communicating via Serial from laptop to Arduino UNO and trying to print the values coming into the sketch. This had worked previously. I have a feeling it has something to do with OS X 10.11 but am not sure. Any ideas are welcome!

I'm getting the error:

Arduino: 1.6.10 (Mac OS X), Board: "Arduino/Genuino Uno"

Error opening serial port '/dev/cu.usbmodem1421'. (Port busy)
Error opening serial port '/dev/cu.usbmodem1421'. (Port busy)
processing.app.SerialException: Error opening serial port '/dev/cu.usbmodem1421'.

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

Could you post your code? I will try to recreate the problem.

z1snow:
Serial.println is no longer printing to the serial monitor. I am communicating via Serial from laptop to Arduino UNO and trying to print the values coming into the sketch. This had worked previously. I have a feeling it has something to do with OS X 10.11 but am not sure. Any ideas are welcome!

I'm getting the error:

Arduino: 1.6.10 (Mac OS X), Board: "Arduino/Genuino Uno"

Error opening serial port '/dev/cu.usbmodem1421'. (Port busy)
Error opening serial port '/dev/cu.usbmodem1421'. (Port busy)
processing.app.SerialException: Error opening serial port '/dev/cu.usbmodem1421'.

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

Do you have something else running that uses the port (it might even be the upload process). You are sure that '/dev/cu.usbmodem1421' is indeed the Uno? Can you upload sketches? Not a mac user so will not be able to help further.

ithinkso:
Could you post your code? I will try to recreate the problem.

I doubt that it's the code; sounds more like a mac issue.

Had you tried to install the drivers?
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