I refinanced as well in 2020. I put "0" for the first mortgage, then I had to retype the date it was paid off in the box to the right. Then I put the refinanced amount and left the box to the right blank.
When I did this the "0" value didn't give me an error to continue. I've tested it multiple times and each time I enter "0", I had to re-enter the date it was paid off.
