Rejected return

My daughter filed for the first time on her own this year.  Just received notice that the return was rejected because the SSN number has been used on an accepted return (code 515-01).  She had to amend a return last year because I accidently claimed her as a dependent even though per IRS she was not.  I did not receive any deductions because she made her own money.   We decided to amended her return in February because she was mistakably marked as a dependent on my return, They received the amended return 4/2019 but it has still not been processed.  Could this be the reason why her return was rejected?  Or is she possibly a victim of identity fraud.  This is really bad.  Please help.

Update - I found out more information.  Amended return is showing as adjusted.  Pulled the transcript and 2020 tax year is showing amended return received 4/2020.  Updated 1/19/2021 with code 290 (says no tax return filed)  and $0.00 in the amount column.  At the top of the transcript it shows tax period December 31, 2020.  Could the processing of the amended return in 2021 be the reason for the rejection?  Any info would be greatly appreciated.