Hello @sherryrao1 ,
I think we are already working on one support case for this one. I am outlining the details for reference here as well:
1. Customer Attributes are available in AA and Target only.
2. The uploaded IDs are not synced currently so uploading them via CS will not be of much help here.
3. In scenarios where ID sync is not present prior to the data upload, AAM is a way in!
4. There is similar data file upload feature in AA but it will incur server calls,
4. If you could share any insights on the issue with FTP server/S3 bucket then I can assist you with a better resolution.