There are many reasons email would have issues. First verify system email works on your Joomla install. System - Global Configuration - Server tab. Eshop will use whatever email system you have set up in Joomla, if that is working, your order emails should work - unless they are getting caught in a spam or junk filter.
The following user(s) said Thank You: Giang Dinh Truong
I just want to update here the reason of issue because the wrong setting in the PayPal account. I helped Sharon via ticket system to guide him turn on the PayPal IPN from the account and all was resolved and working well now.
I just wanted to let everyone know how exceptional your support was with the issue that we had.
We are in the UK and you were helping us first thing in the morning. As you advised which steps to take we were able to action them immediately until the problem was resolved.