Thanks Terry.  You understood correctly with couple of corrections on my part and subsequent results.

Both parents tax return and daughter's were for 2018. Parents was filed last year and accepted but daughter trying to file 2018 now because it was being rejected last year since she tried after parents filed.

I tried several fixes on daughter's 2018 return but it kept rejecting but amazingly got accepted after I removed the mother from daughter's return and filed her as head of household with only the father shown as dependent. Reduced refund but got it through since her refund was significant anyway and did not want to delay for manual filing and eligibility for Corona tax relief refunds.

It's also interesting that the problem did not occur in her  2016 and 2017 tax returns which were accepted with both parents and as HOH.  Same SS numbers were used in all 3 years for all three persons.