I'm assuming that Terry solved it by using the correct email setting as in the thread.
You'll need to confirm whether any emails at all can be sent out from your DNN instance by using something else like the bulk email module. If that works, then check all email addresses in the store and also try a different account. Check your DNN logs, check the store logs in the portal folder and try sending email notifications manually by editing an order and using one of the notification buttons. Check your spam folders, email server logs etc.
There are many places an email can vanish, so you just have to start at the beginning of the process and work through it.
Regards
Rob