The 1095-A is ordinarily no longer required, unless you have marketplace insurance, so that is odd - unless his employer coverage is from the marketplace?

That is may be whole different matter. I have a client who was covered by their parents marketplace policy and had 0 responsibility and I filled the 8962 out properly - even consulted with an ACA specialist at the IRS and Proseries technical support twice. Still rejected - a total of 4 times. I finally did a detailed written explanation and attached to return as pdf and it was almost instantaneously accepted by the IRS.

If all else fails, as it did in my client's case, even after expert advice, try the attached written explanation.