I had some issues with TurboTax Online given the wrong decision about whether my 23 year old full time student, live at home son was a "Qualifying Child" and afforded me the ODC credit.
Seems TurboTax has corrected that (for the most part - there are still some odd quirks with the screens when you edit a dependent but it still come up with the correct answer).
In trying to get to the bottom of this, I fould that the IRS is not really clear/correct with their various Interactive Tax Assistants (ITAs).
Compare the two:
https://www.irs.gov/help/ita/does-my-childdependent-qualify-for-the-child-tax-credit-or-the-credit-for-other-dependents
and
https://www.irs.gov/help/ita/whom-may-i-claim-as-a-dependent
See the screen shots in this existing thread:
https://ttlc.intuit.com/community/taxes/discussion/re-ongoing-issue-with-dependent-child-odc-status-in-turbotax/01/3445978#M36072