CHECK THIS ENTRY: Form 8962: Your calculations could not be completed. Reference code: 6-399-259 Error

You will not be able to prepare Form 8962 on the Free Edition. If you are using a TurboTax Online product, you will need to upgrade to The Deluxe edition or higher.

If after upgrading to the TurboTax version you are still getting this error, remove the form altogether and enter it again. This usually fixes this error. 
 

You can manually review a section or delete a specific form/worksheet in 2 different ways. To manually review a section, you will manually go there and click the trash icon next to the section you want to remove.

It is not recommended to delete a form or worksheet directly; instead we recommend to go over each specific section of the return from the beginning, double-check your entries and answers, and remove any necessary information. 
 

To delete that specific Form, see the applicable link below
 

How to Delete a Form on TurboTax Online

How to Delete a Form on TurboTax Desktop

The error that you are getting is due to having Form 1095-A in your return and not completing Form 8962 completely on your return.  The error could be because you started entering something for Form 1095-A or accidentally selected a box for it.  If this happened the program would have started calculating Form 8962.   

Since she didn't receive insurance through the marketplace, you don't need anything completed for either Form 1095-A or Form 8962.  Follow the instructions from NicolleR1 and delete Forms 1095-A and Form 8962 from the return, if the program started them. 

If this doesn't clear your error, you could also try troubleshooting your web browser.  Turn off any pop-up blockers, use a different web browser, delete your browser cookies.

@khadijahdp 

Follow these steps to remove the connected forms:

1. In forms mode
2. On the left hand side at the top, select open form
3. Type 8962 into the search box
4. Select the form- highlight it
5. Select Open Form in the pop up box
6. Now you should be able to see the form.

Follow the above steps again for 1095-A

Now you should have both forms as part of your tax return. Give them a review and make sure there is no information pulling from somewhere else.

Once the forms only have each other you will delete them. 

1. Delete the form 1095-A, then the 8962.
2. Check to see if either form has reappeared. If so, the program is holding the information for a reason and any cells need to be emptied- ties cut with any other forms/ information.
3. delete forms again -if needed.
4. Save your return while closing the program.
5. Update the program
6. Open
7. Continue on with your return.

@nv2089 

You can normally delete the forms that TurboTax has prepared from your opening the screens that support them. If you are using TurboTax Online, see this help article and below for the steps to Delete a Form: 

1. Open or continue your return.
2. On Tax Home, select Start, Continue, or Pick up where you left off to enter your return.
3. In the left menu, select Tax Tools and then Tools.
4. In the pop-up window Tool Center, choose Delete a form. (Look for any form or worksheet relating to Medical expenses.)
5. Select Delete next to the form, schedule, and worksheet in the list and follow the instructions.

If despite live sessions with Support you are unable to resolve this issue, one more thing you might try (I didn't see it mentioned) is to try another browser. Some users have reported success with Edge when their usual browsers didn't work.

Otherwise, if you still have no resolution, see this help article for information about refunds. TurboTax Online products are normally non-refundable, because you have the choice to prepare your return without paying upfront; however, you could request an exception if there is an unresolvable issue.

@SFV