The guy at the Help Desk is absolutely wrong. If the son’s file doesn’t show the father as a disabled dependent then the return will certainly fail on efile…almost guaranteed. Realistically, the documentation needed to be sent in prior to tax season so the son would have been set up for the claim. What you’re going to end up doing is e-filing the son’s return without the claim, and then sending in for an adjustment. Otherwise, you are going to paper file the return.
Any of these that I have (child claiming a parent) show up in the Represent a Client as eligible to claim the Disability for then they show the parent or sibling’s person’s name.