If the applicant did not receive the invitation e-mail, you should recreate the invitation and send it again. It’s possible that one of the fields, such as the e-mail, was entered incorrectly. If you continue to have issues, contact the eGrants help desk at 1-800-942-2677 between 8:00 AM and 8:00 PM Eastern time, Monday through Friday.
See also:
How will I know whether the applicant has received the invitation and registered?
What should I do if the e-mail address is invalid?