I'm adding an additional user so they can upload some forms, but that person says they never get the email to have a user name and pswd

If you are referring to a sub-user account, this will only send an invitation to the email address you entered. This means that they have to signup an account using the invitation link according to their preference. After the registration, that account will become your sub-account and they will be able to access the form you've shared. 

If this isn't what you mean, kindly elaborate the question further.

Thanks!