@vflorio94 this error can happen frequently, it happens when the url is available, but the board doesn't accept connections. Or when the board is starting, it might take a few seconds to be able to connect to it. You don't have another connection to the board, right? (And I assume you have tried hard resetting, disconnecting power then trying again)

@jmarcelino Hi I was trying the code on Leo Gaggl's blog page . Cheers Sean

@w0run try Visual Studio Code (https://code.visualstudio.com/) with the PyMakr plugin. Works very well.

@jmarcelino That fixed the problem! I did not have a jumper on the RX pins. By demo application I mean that when I plug in the board the green LED flashes, followed by the blue LED every 4 seconds. Thanks a lot for your help!