Can’t Assign Specific User post function on the Create Issue Transition on a subtask.

[Josh Pope]

I want to assign a user on a subtask creation with a post function on the create transition.  The assignee is not registering when the subtask is created.  I have ordered the post function as described in this knowledge base article but this doesn't seem to apply to a subtask:

https://confluence.atlassian.com/jirakb/can-t-get-assign-to-current-user-post-function-to-work-on-the-create-issue-transition-455542268.html

Any help would be much appreciated!