Hello @MichaelCo36 ,
To provide more clarity. Please share the SS of the DV360 Destination. I would like to see the segments mapped to DV 360 and Audience List in DV360 Platform.
Just to provide a quick workaround. You should try removing the segment from the DV360 manually. As your organization has stopped using AAM. This is the only way I see as of now.
Regards
Akshay