Some Salesforce Fields Missing when Connecting to Data from Tableau

Depending on the specific field and object, the issue may be resolved in one or all of the following ways: 

Option 1

Create a connection to the correct table, where the desired fields are located. This might require using a join or creating a custom connection. For more information, see Connecting to Salesforce Data Source.

Option 2

If the field type is defined as a formula in Salesforce.com, it will not import due to limitations with the Salesforce API. You must connect to all of the tables that contain the fields in the formula and use that data to create a calculated field.

Option 3

If the field is defined as a Long Text Area, you may contact the Salesforce administrator to see if it's possible to create a second field for Text field and pragmatically copy contents from the original Long Text field to the new Text field as a possible workaround.
Note: “Long Text Area” fields are only excluded if their defined maximum length in Salesforce exceeds 4096 characters.
This limit applies to the field’s definition (capacity), regardless of the actual number of characters stored in the field for any given record.  For more information, see Errors during extract.