I'm amending my filed 2020 return but Turbotax doesn't start out with a zero balance

I'm amending my filed 2020 return but Turbotax doesn't start out with a zero balance.  When I bring in the return to be amended, and I click on continue (after the 3 steps are listed), it says I owe tax even though I haven't made any revisions.  It should start with a zero balance.