Arduino not 'listening' any more


Hi all,
I could really use some help here:
Background: I am doing my first grow-cycle and since I couldn’t get the GRO-UI up and running I was using the Arduino serial monitor to manually control the PFC.
Since the amount of data was getting very big (and responses therefor very sluggish) I quit the monitor and wanted to reboot it again. Unfortunately since that moment the monitor would not listen to any commands that I gave (using the VNC remote desktop). IT sends strings of data (no measurement data, only status data of the actuators) and I cannot change anything. I cannot change to ‘newline’ so everything comes in horizontally and I cannot engange or disengage any actuators any more.
Note: there is a sketch called ‘sketch_sep11a’ active in the Arduino app. When I want to send to the arduino I get an error (see:

Any suggestions what I can do now to either get met monitor working properly again or get to a point that I can use a script (or so ?) that does all the actuator changes automatically ??


Update: I f have connected the Arduino directly to my Mac, and the monitoring seems to be working fine now. Could I have screwed up some properties in the RPI Arduino software that could have caused this ?