Did you set up a connection following these guidelines Salesforce - Tableau? Where you able to drag a table onto the canvas? Tableau only supports extracts so it will force you to create one and only once this is created will you be able to refresh.
Thanks for the reply!
Yes, I did. It is all working fine in terms of my data is there, and I am able to create the visualizations I want. And it says, 'extract created (the date I created the workbook) - I am just not able to refresh it ... the button for refresh is greyed out see screenshot below) and when I go to Data - > Refresh Datasource nothing seems to happen. Also everytime I close the workbook and reopen it and try to access the data, it tells me to log in to salesforce again which is another reason I think it's something to do with the API settings in Salesforce???