Underpayment Penalty - Annualized Income shows total of ZERO

[WillieD]

I did a Roth Conversion on Dec 26 so I need to do the calculations for Underpayment Penalty.  I went through it once but made some errors so going back through it again.  When I get to the page to enter income for the 4 periods, TT is showing my adjusted Gross income for the last box (full year) as "zero" (word) - it is not adjustable.  I don't know if it is treating it this way becuase I did it once already.  How do I get it to reset and pull up the full number for the box for the full year.

[WillieD]

Update:  I don't remember which ones, but I changed some numbers on the form and then went back and it allowed me in again.