When responding, be sure to include either the Tax Return Transcript or a complete copy of the latest federal tax return, including all schedules, W2 forms, and 1099 forms, as applicable. For citizenship, a photocopy of a certified copy of birth certificate, or copy of passport.
Since they want the applicant's passport back too, expect success this time, if the documentation provided is acceptable.
I'm sure you are shaking your head and asking "why?" since you say you provided this already. I don't know, but my best guess is what you sent the first time was either incomplete, or didn't get matched up with the rest of your file.