I received an error 'AAO : UMRN(20210608157528)SEGMENTNADLINE26ELEM3164(6.0)MAND ELEM MISSING'. What does it mean?

I received an error 'AAO : UMRN(20210608157528)SEGMENTNADLINE26ELEM3164(6.0)MAND ELEM MISSING'. What does it mean?

Missing consolidator CITY NAME.