Your issue will be that the other parent had the ACA insurance and the child is listed on her 1095-A form.
Now listen carefully ... this can be tricky. You must both enter the 1095-A on both returns however you get to decide how much of the premium tax credit is allocated to each return. The total combined must be 100% ... so she can take 100% and you take 0% ... or 50/50 ... or any combination that works best for you ... play with the percentages to see which way is best overall.
