There is a current issue with Form 8960 that has been reported.
See https://ttlc.intuit.com/community/turbotax-help/help/turbotax-online-error-form-8960-worksheet-your-...
You can contact Customer Support (link below) during regular business hours for more information.
https://ttlc.intuit.com/community/using-turbotax/help/what-is-the-turbotax-phone-number/00/25632
