When you have all zero's in a row (i.e. no amounts) - you need to leave the boxes blank instead of entering the zeros.  You should be able to leave it blank once you delete ALL the zeros (you might still get an error when you only remove one zero from each box in the row).  The program will read the blank boxes as zeros and calculate the credit accordingly

Note:  If you did an import of your Form 1095-A, then you may need to remove the import and re-enter manually.  If you go back into the health insurance section you should see a trash can icon or delete button next to your Form 1095A) that you can use to delete the form, the re-enter manually instead of importing, leaving off all the zeros.