Ensure that you have the permission. Also please check GetActivityParties is present in your webresource and you have tagged it correctly to this form.
P.S. The Azure Bot Service engineering team confirmed that there was an intermittent disruption in the service causing bot creation failures.
At this time, the issue has been mitigated so please retry your create request. If you still having problems, please do let us know by opening a new issue: https://github.com/Microsoft/BotBuilder/issues/new