Arduino set up for work with Octave (Matlab) then disconnected

Hello everybody,
I just set up Octave for work with an arduino.

arduinosetup worked fine.

scanForArduinos yielded

*{
[1,1] =

scalar structure containing the fields:

  port = \\.\COM4
  board = uno

}*

But a=arduino just gave me the error message

a =
arduino object disconnected

And a new scanForArduinos didn't find any.
I tested several boards on both USB ports of a Microsoft surface 7 running Win10.

Has anyone encountered and maybe solved this problem?

@stynwe, your topic has been moved to a more suitable location on the forum. Installation and Troubleshooting is not for problems with (nor for advise on) your project :wink: See About the Installation & Troubleshooting category.