Hello Liam.

Sorry for the late response and thank you for your purchase.

Issue with email notifications could be caused by several reasons:

1. Your hosting provider is blocking all 3rd party settings, and only allowing their SMTP (or other) settings. 

2. Your website has PHP version less than 7 

3. The credentials are not correct 

4. There's something else blocking the notifications from being sent. 

5. If you're using Gmail, please make sure "Allow less secure apps" is enabled.

Please check these points, and let me know if you were able to resolve the issue. If you're still not able to resolve the issue, we'll need to remote into your website, and see what's going on.

If that's the same, please provide me a temporary WP-admin (administrator) user for your site where this happens, so we could log in and take a look ‘from the inside’ as that’s the most efficient way to see and resolve the issue. 

We do not interfere with any data or anything else except for the plugin (in case that’s a production version of the site), and of course, we do not provide login data to third parties. 

You can write credentials here just check PRIVATE Reply so nobody can see them except us.