The absence of a date of entry stamp is the likely reason your child's ITIN application was rejected. The requirement applies to "certain dependents" per the W-7 instructions. A spouse is not a "dependent" to the IRS. See Proof of U.S. residency for applicants who are dependents on page 4 of the instructions.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
