Joost,
Activating/deactivating polls requires a separate URL. From our internal API documentation:
PUT /api/activation
Required params
`type`
String that represents the type of activity.
Currently supported: "poll", "survey".
`uid`
Unique identifier String
Returns 400 if the `type` is invalid.
Returns 404 if you are not permitted to activate the Activity, or if the activity does not have an owner.
Returns 204 if activation was successful, even if it was a no-op.
For an example, I recommend using your browser's web inspector while manually activating a poll.
Mike
Poll Everywhere Engineering