Some candidates have not uploaded a resume in their job application. There are several possible reasons for this:
The candidate did not have a resume handy when applying: he/she may be using her phone at the time and did not have a resume. Automated emails will be sent to the candidate to upload a resume within 3 days.
Disingenuous candidate: some candidates apply for jobs with no intention of getting a job.
If unsure, you can try contacting the candidate to ask for a resume.