Errors & Troubleshooting

Occasionally the editor or app you are using will throw an error. Common errors are listed here with a description of what they mean and what you can do to resolve them.

Why does MicroPython on python.microbit.org and Mu work differently?
The MicroPython editor hosted on the http://python.microbit.org website follows a different update cycle to the Mu editor. Both MicroPython on the webs...
Fri, 15 Feb, 2019 at 12:24 PM
Why can't I use the Bluetooth and Neopixel packages at the same time?
Unfortunately, It's not currently possible to do this because the NeoPixel library needs fast uninterruptible timeslots to get accurate data sent to th...
Tue, 26 Jun, 2018 at 12:01 PM
Incorrectly named .hex files fail to upload
You may find that the .hex file fails to be flashed to your micro:bit, resulting in the file briefly appearing on the micro:bit device, alongside a FAIL.txt...
Tue, 16 Oct, 2018 at 9:01 AM
makecode.microbit.org doesn't load on Chromebook
If you find that when you load the MakeCode Editor that elements of the editor are missing or it gets stuck loading a new project: that you meet the firewal...
Tue, 23 Jun, 2020 at 10:51 AM
Search not working in the Makecode Editor/Can't add extensions
When tryting to add an approved extension, you may be presented with a message saying 'We couldn't find any packages matching...'. T...
Tue, 23 Jun, 2020 at 10:49 AM
0kb .HEX file
If your .Hex file appears to compile and download, but results in an empty (0Kb) file it is likely due to lack of storage on your device. If you are downloa...
Tue, 5 Mar, 2019 at 9:14 AM
Program Error: sim error: failed cast on null
Description This error occurs when in the MakeCode editor simulator when it is trying to process the program and there is an error in the code. This is usu...
Thu, 6 Feb, 2020 at 3:37 PM
How to get the current program off the micro:bit
There may be occasions when you want to take a look at the programming that is running on the micro:bit or if you have misplaced the original program. To do...
Thu, 27 Aug, 2020 at 8:16 AM