Fields are not available to map using Data Loader
|Knowledge Article Number||000171207|
|Description||When importing or updating records using Data Loader, some of the fields are not available for field mapping.|
|Resolution||Check the Fields on Field Level Security by Profile or by Fields.
If the field is hidden, this will not be available via the Data Loader for mapping.
FLS will grant a user access and visibility on that field. Once confirmed, modify the Field Accessibility and Permissions for that particular profile.
Also, Auto-number, Formula, and External ID fields will not show up in the list of available fields in the Data Loader for mapping. Since Auto-Number fields, Formula fields, and External ID fields are read-only fields that are not create-able or update-able.
For more information see Auto-Number not available as external ID in Data Loader?
Any Fields which are not added to Page layout, those fields will not show up in Data Loader for mapping. Hence,all the fields must be added to any of the Page layout for Mapping.