Stop going back to that section and the amount will not disappear.  Now for the credit ... did you enter in all your income yet ?   Until you do the credit will do you no good.   If you have entered in the income then review the actual tax forms to see how the credit is being computed and why none is deductible this year. 

How do I preview my TurboTax Online return before filing?

You can view your entire return or just your 1040 form before you e-file:

1. Open or continue your return.
2. Select Tax Tools in the left menu (if you don't see this, select the menu icon in the upper-left corner).
3. With the Tax Tools menu open, you can then:
• Preview your entire return: Select Print Center and then Print, Save, or Preview This Year's Return (you may be asked to register or pay first).
• View only your 1040 form: Select Tools. Next, select View Tax Summary in the pop-up, then Preview my 1040 in the left menu.