I believe I found the reason and (hopefully) the solution. After poking around, I found the "Joint Filing Credit Allocation Worksheet" On this sheet it indicated that my Ohio adjusted gross income was a negative number. This was due to allocating all of our HSA contribution to me and after deducting that amount, I had "no Ohio income"
After splitting that allocation between both of us, my Ohio AGI is now more than the required $500.
