I'm trying to finalize my 1095a review but it won't accept my modifications. What am I doing wrong?

I will suggest you delete the Form 1095-A and then re-enter it. 

To remove the form, here are the steps:

In TurboTax online,

1.  Sign into your account, select Pick up where you left off

2.  Select Tax Tools, click on the drop down arrow

3.  Select Tools

4.  Under Other helpful links, choose Delete a form

5.  Select Delete next to Form 1095-A / Form 8962 and Continue with My Return

To re-enter, follow here:

• At the right upper corner, in the search box, type in "health insurance" and Enter
• Select Jump to health insurance
• Follow prompts

If you are entitled to claim a Premium Tax Credit on Form 8962, it will shows on Schedule 3 line 8 and Form 1040 line 31.