Why aren’t the people I invited getting system emails?

First of all, check if the email address you’re trying to send to is correct. Secondly, check with the recipient, and make sure their spam isn’t grabbing ahold of it. Lastly, make sure you’re clicking ‘submit’ when adding users.
When you add new user and he didn't get the email invitation you can resend it. To do so please follow below steps:

1. Go to Account & Settings, then click Edit Users.
   
   
   
   
2. Click Edit on user's icon.
   
   
   
   
3. Click Resend Invitation Email.
   Note: The button works for new users only, does not show up if the user already logged in at least once.