Hi,
Are other emails being sent by your website ?
First, go in the menu Customers>Emails history. Do you see the emails that should have been received there ?
If yes, then HikaShop sent the emails to your email sending server and the problem is on that server. In that case, you'll probably need to check with your hosting company support for what's going on with the email sending.
If no, then go in the menu Orders>Orders.
Is the status of the orders automatically changed from created to confirmed after the payment ?
If no, then the issue is a payment notification issue between your payment gateway and HikaShop. It can come from many things. We have a documentation on this here:
www.hikashop.com/support/documentation/i...or.html#notification
If yes, then go in the menu System>Emails and check that the emails are not disabled. It could also be than an error happens while the email is being generated. This could happen due to a wrong customization of the email for example. Did you change something in the emails before the problem happened ?