Press 'Disconnect' in OctoPrint. Then open the setting and go to firmware update plugin. There select the port. That's why you can to disconnect. The port can only be connected by one application...
It should be in this status (so not connected with the printer) but of course the USB should be plugged in the Rumba.
Huge thanks for the ALL the help @Alex9779 and @Rob Heinzonly I flashed it using the file you attached in the post and with the Firmware Updater Octoprint Addin, it worked perfectly! Bed currently sitting @ Z:300 I was not aware that I needed to disconnect the server. Props!!!!
Yes that was a serious indefinite antecedent (like pull the USB cable vs. software disconnect). The first time I saw this I was also confused. Then as a software developer I was more confused as to why the plug in doesn't call disconnect, update and reconnect, since that is proper UX, but hey, at least it works...
Sorry if this has been answered, but is this the OctoPrint Firmware Update Plugin that you are talking about: https://github.com/OctoPrint/OctoPrint-FirmwareUpdater
That's the one Ray! It worked great just be sure to use the Disconnect as seen in Rob's screenshot in this thread.
@Alex9779 and @Rob Heinzonly also had some great screenshots and info on this thread: http://forum.e3d-online.com/index.p...-would-you-like-to-see.1194/page-2#post-11092