This error message will appear in the makecode.microbit.org editor if the editor cannot connect to another cloud service, for example downloading an extension. The message might appear behind another window telling you that the extension is being downloaded. Sometimes this is due to the service throttling connections to prevent DoS attacks. See this issue on GitHub for further information.
- Make sure the resource that you are trying to use is accessible to the outside world. Try checking the browser console log for errors:
- Try using a different computer to see if you still get the error
Open a support ticket or if you have a Github account an issue on pxt-microbit