Hi
postactivation notification do not works
I work around and use change status notification and set to work when active status appear - its works correctly
Refund notification do not works - I use change status to refund notification
Its looks that you have general problem with notifications working on invoice satus change (for subscriptions status change its works)
Probably if I change notification definition to work with status inactive it will work, but I am not sure if refund is only case which can set subscription to iactive state,