This is because the data has been "Extracted", so Tableau is asking for the original file to show you the structure.
Your best bet is to simply right click on the extracted data source in your workbook and choose "View Data" -- you can then export to Excel or any other data tool of your preference. This is probably the easiest way to see the structure of the data in the Extract file.
Highly appreciating your response and help. I got your point and its really helping.
However, I have a small question. In the said method, I will not be able to see how many tables has been used and type of join. Is there any way to know this?
This is a standard prompt by tableau when you click on "Edit Data Source" or on "Data Source" for a .twbx file.
Probably because of the reason when you click on edit data source tableau will try to trace the actual source file location and as it will be not reachable (as user is different), tableau will ask you to redefine the path.
Step 1 : Navigate to Data menu > Data Source (generally last option in the drop down) > export data to csv.
(If you only want to view data this is enough, if you need to see the joins then continue with below )
Step 2 : Convert above exported csv into the file type of the original one (you can identify this based on when you click on data source, check what type of file it is asking)
Step 3 : Click on the Data Source navigate to the above saved file and you can now see the Data Pane window
Thanks for the nice answer. Its really helpful.
However, the biggest problem I am facing is to see the join types or number of tables which has been used to create the dataset. Unfortunately probably Tableau has not given that facility to us.