I checked again the code, the WooCommerce source code, the PayPal payment gateway source code and everything seems OK.
I don’t know what are your technical skills, however I will try to explain to you how it works.
When the plugin sees that its Braintree request succeeded it asks WC to complete the order. By doing this the WC updates the order status which in turn triggers an special event (a hook) which will start sending emails based on the event type (in this case is an order_status_completed
).
So see, this is an automatic flow that normally triggers when someone (the plugin itself or even your own hand) completes the order status.
Now, this being said, you may test the flow regardless of what the plug-in does or does not. Of course, I don’t recommend you to use a real order (ie. your real customer order) because it will flood him/her with unsolicited emails which might confuse him/her. Instead you should create an order for yourself (in a test environment or even on production, with care). When this is done just try to set manually the order from Pending payment
to Completed
. This should fire the event I mentioned earlier which in turn will automatically send an email (to the buyer, hopefully your test email and to the seller, ie. yourself).
If this works then I would expect it works even when the event is fired by the plug-in itself instead on your manual action.
Does it make sense to you?