Hi,
You say "was the issue". Does that mean that the problem is fixed on your end ?
The first thing to check when you have a problem with the emails is the menu Customers>Emails history.
If you see the emails there but not in your inbox, HikaShop sent the emails to the email server.
So then, the best is to look at the logs of the email server you're using (maybe only your hosting support can do that and in which case you need to provide them the details of that email from the Customers>Emails history). There, you should see why the email couldn't be sent to the receiver email server and if it says that the email was sent successfully, then it will mean that the email was discarded by the receiver email server (spam, wrong email address, email box full, etc).