If both admin and customers don’t get email notifications from payment terminal there is a chance that your hosting provider is blocking those emails for some reason. 

Here’s what you need to check:

1. Check your/your customer’s spam folder – emails may have went there.
2. Open support ticket with your hosting provider and ask them if sending emails through php mail() function without authentications works, or are they blocking it.
   If your hosting provider requires you to use SMTP authentication for emails coming from your site – we suggest installing 3rd party plugin like Postman SMTP to easily setup SMTP authenticated email delivery per your hosting provider instructions.
3. Our payment terminal is using wp_mail function for sending email notifications, do you have any issues with receiving other emails from your site? If you don’t have any issues with any other emails coming from your site – you may need to adjust the sender name and sender email address in plugins/authorize_net_payment_terminal/terminal/authorize/form.processing.php  lines 243 and 439 – by default it will send from [email protected] with the name ‘Authorize.net Payment Terminal’ – change it to whichever email address currently sends emails from your site which you receive without issues.
4. If none of the above will help – we suggest to use 3rd party transaction mail delivery service like mailgun.com (10,000 emails free every month) – all you need to do is install Mailgun for WP plugin, create an account (add 2 DNS records to the domain name), add your API credentials to the plugin and it will work fine then – all emails from your site coming through wp_mail will be sent/delivered through mailgun.com service.

If you will require further assistance – please open support ticket.