Customers Not Receiving Emails

I’ve got an issue where by a customer will place an order, pay via PayPal (my only accepted payment currently) which changes the order status to “processed” and then receive an email stating that we have received their order.

We then package the order, update the shipping / tracking info and change the status to “complete”. I have the 'notify customer" checkbox ticked when I do this so it should send an email to the customer.

It doesn’t appear to be sending the customer email yet I get a copy. I’m not getting any error messages when I change the order status.

Any ideas why this may be happening?

If you use new email editor, please make sure that the corresponding template for the "complete" status is enabled