It was rejected for the Social Security number you entered for one of your dependents. You must enter exactly the same name and Social Security number that is on the current Social Security card for the dependent.
Click on My Info on the left side of the online program screen, edit the dependents and review your SSN entries for them.
If everything is correct and the IRS continues to reject your e-filed tax return, you will have to print and mail the return.
See this TurboTax support FAQ for how to print and return for mailing when using the online editions - https://ttlc.intuit.com/turbotax-support/en-us/help-article/printers-printing/print-mail-return-turbotax-online/L5bwuqXGy_US_en_US?uid=lrs4rq8g