Cannot toggle live and upload button on my custom device


I am using my custom device established on the extension builder. When I try to toggle the live and upload button, the button will freeze with the circle rotating. I didn’t change anything on .mext file. I believe there is an update that I did not get noticed which causes this problem.

PS: It works fine yesterday afternoon.

Is there any way that I can resolve the problem? Or can I downgrade to the previous version?


Hi sundong212,

Here are some info we want to know:

  1. Do you mean there is no such problem with the previous version of the mBlock 5 software? May I know the version number which works?
  2. You mentioned that it works fine yesterday afternoon, may I know what you have changed after that time?
  3. What is your custom device?
  4. Could you send your extension file to us? You can send it to email address:



Thank you for the reply.

  1. The extension file finalized around Aug 28th. It has been working fine until yesterday, October 9th, New York time.

  2. Yes, it works fine on October 8th afternoon, New York time. I didn’t make any changes since Aug 28th.

  3. The custom device is actually an Arduino UNO

  4. I would like to send you

    these two photos. Let me know if you would like to see photos with English.

Here is an interesting I found out just now. I changed the ‘supported mBlock version’ from only including 5.0.1 to including Latest. And I cannot import the .mext file to the mBlock software. A notification pops up that says .mext file version not supported.

Thank you very much!


Hi sundong212,

For the “supported mBlock version”, please don’t check the latest, just check the mBlock 5.0.2. The latest is a version that is not yet supported. If you check it, you won’t be able to use it.

For the original problem. I have confirmed with our engineer, there is no updates for the environment during this period. Here we need some more info to locate the cause:

  1. Could you please send the extension file (the .mext file) to me.
  2. Please send us the error message. You can call out the console to see the error message refer to the following steps:
    Step 1: Click on Preview on picture below:

    Step 2: Press ctrl+shift+i to call out the console to see the error message


I cannot call out the console, could you give me a hint that how to do it with Mac?
Plus, after I clicked the preview button, how can I get the latest published .mext file.
Sorry, I am pretty new to this.

I have sent you the file with the subject of this topic name to Let me know if you need more resources.


Hi Dongsheng

Thanks for sharing the file.
Our engineer has tested it and it works (can toggle the live and upload) on web version mBlock 5.
But can’t toggle for the PC client side mBlock 5 software due to that the PC side mBlock 5 software temporarily doesn’t support live mode for the third party users.
May I know did you test it on the web version mBlock 5 or PC side mBlock5 software?

Besides, the next version mBlock5 software for PC side will add the function of supporting live mode for third party users.



Thank you for the testing.
I cannot test it on web mBlock5, because it showed up an error message saying it doesn’t support the format.

For the live and upload mode, I am actually trying to using Upload mode.
But it will keep this state forever34%20AM

Could you guide me on how can I test it on the browser?

Thank you very much!


Hi sundong212,
We tested with preview in extension builder, which works.
The error (your first picture), I am afraid you were trying to drag the file to web version directly. Actually this doesn’t support drag in web version.

Please try Chrome browser if you didn’t. Then if the issue happens again, please press ctrl+shift+i to open control interface, and choose console, take a screen shot here for us when it states at below:


  1. I am using ‘My device’ instead of ‘My extension’. Does this cause this problem?
  2. My question was: can I call out the console in the application(not the web one)?

Plus, do you have a tech support Wechat or other communication approach? The forum communication does not have any efficiency.

Thank you very much!


Hi sundong212,

  1. yes.
  2. yes, should in web one.
  3. for better communication, you may join in this facebook group:
    Or scan this QR code and reply "扩展” or “extension”, then you will be added to developers group.