Upon further thought, not sure why you put "tax refund" in parentheses.

"cannot get it to calculate the credit (tax refund) "

I don't think it's a refundable credit.

In my simple test for Form 1120H filing, it was a GBC (Form 3800) carryforward only. I have only worked on a few 1120H returns and that was half a dozen years ago, so I don't remember what the difference is between 1120H and 1120 filing for a HOA. What happens when you switch to regular Form 1120?