What does the error "Reject Code FDI_8615Line7Box_Err" mean?

If the Qualified Dividends and Capital Gain Tax Worksheet, Schedule D Tax Worksheet, or Schedule J (Form 1040 or 1040-SR) is used to figure the tax, you must check the box.  If not, you must un-check the box. 

I had the same problem. My return was rejected with this error message. Not sure of the solution? How did you fix it?

I received the same rejection error.  What Box needs to be checked, to use the Qualified Dividends and Capital Gain Tax Worksheet?  For some reason I have two Form 8615 Line 7 worksheets, with 2 different resulting amounts.

On 03/20/20 the update on Form 8615 was installed on the Online version of TurboTax. You will need to back through the Form 8615's in the software to have the updated calculations to take effect. You should be able to e-file your return without being rejected.