Don't believe PTO identifies the dependent number on the return for you to review.

If you are certain all the names and SSNs are matching what is on each of their social security cards, your client should call the SSA at 1-800-772-1213 to verify the details on the SSA's records. In case the SSA's records need to be corrected, it will take about 2 weeks for the update to be reflected on the IRS' system before you can e-file with a match.

Before contacting your client to have him/her call the SSA, double check first that you have entered the last name(s) in accordance with what's on the social security card.  PTO would then convert these based on the convention used by the IRS, particularly if the name includes punctuation, special characters, or certain suffixes. See Individual Name Control bookmarked with this link for more details:

https://www.irs.gov/pub/irs-pdf/p4164.pdf#%5B%7B%22num%22%3A771%2C%22gen%22%3A0%7D%2C%7B%22name%22%3...

[Edit: Omitted to mention, as an FYI, that the IRS only matches the first four characters of the last name against the SSN.]