Now the cause of this problem has been identified: There is wrong information about the Request data format on Aspera Faspex API v4 developer guides about this Create a New User endpoint:
https://developer.ibm.com/apis/catalog/aspera--aspera-faspex-client-sdk/API%20v.4:%20Users
There are the 2 fields need to be corrected in Request:
1) "can_send_to_external_email" should be boolean value
2) "user_profile_data_attributes" should be removed from Request
#Aspera#Support#SupportMigration