Why are we getting the message, "Inserts not allowed", when importing data through the Data Import Wizard?
Data Import Wizard
This message will appear during the pre-scan phase of the Data Import when there are new records being created and the staff account does not have profile permissions enabled to create those type of records. Check the staff account's profile to ensure that they have the necessary permissions enabled to create new records.
For information on the various profile permissions, refer to Answer ID 768: Profile Permissions.