My second guess (much less likely since it's not hiding on some obscure worksheet somewhere like the medicare wages box) is that your 1095-A is not linked to the S Corp.  At the bottom of the 1095-A there's a "Business Related Premiums Information Smart Worksheet" where you can double click in the "box" next to "Schedule K-1, S-Corp" and link this form to the S Corp.  You also have to fill in the start/end months at the very bottom.

Rick