does not find my Arduino Uno, but Codebender finds it.

When I connect my Arduino Uno R3 with a USB cable the my Chromebook (Dell Latitude 5400), the webpage can’t find my Arduino Uno R3. It has found it earlier.
If I copy/paste my code into codebender : edu, the same Arduino is found and the code is uploaded and the serial monitor returns information.

Any ideas?

Link to image of error message:

Is codebender a better alternative than this site?