Adding/removing a team member does not trigger an update in PullApprove (status won't get updated, you may get a "x is not a collaborator" error, etc.). This is because it is an organization webhook, and PullApprove currently only uses repo hooks: https://developer.github.com/v3/activity/events/types/#membershipevent

PullApprove is notified if a team is added to a repo: https://developer.github.com/v3/activity/events/types/#teamaddevent
Or if a collaborator is added: https://developer.github.com/v3/activity/events/types/#memberevent