Hi Ruining,
We have the same error and it's really very strange!
Does your trial period expired recently ?
Try this steps:
1) In the Extension Management page, try to Uninstall your extension manually and Unpublish it.
2) Try again to publish your extension as you did from Visual Studio Code (F5).
3) even if you got the "A task was cancelled" error, you'll find your extension published and installed.
.
Please verify my answer if you find my answer helpful. Doing so you'll show other community members that there was found a solution and you credit my help.
.
