Hello,
Thank you for contacting us,
I'm Sravya from Arduino Technical Support Team. It seems that your board is changing port and you have to repeat the process again.
We request you to try pressing the reset button and continue with the instructions in 2.2.2.2 Connecting Matlab To Arduino section.
However,we want to know what you meant by "need power cycle"? Is it connecting the battery to the battery connector on the board?
Have a nice day!
Best regards,