How to solved this serial comunication problem?

Hello. I have a problem with serial communication in Matlab. I am sending information to an Arduino board to control some motors. When I send the information using a Serial monitor, all work perfectly. But when I do it using Matlab I need close the port, and open it again every times that I send something. I thought that could be the buffer and I tried to use the command "flushoutput" and "flushinput" without success. What could be the problem? Thanks in advance

[Walter Roberson]

What happens if you do not close and open each time you want to send something?

What are you configuring as the line terminator?