Asterisk is displayed when Tableau cannot specify single value from given data structure.
In case of blending, it happens very often.
By the reasons
- Your "link" field setting is not defined
- Your data is not supporting to specify single value
I added I few more screenshots with each Data Source I using to show you what I am working with..
Screen shots do not help so much.
If you could attach whole packaged workbook we can work with it.
Could you clarify what is the issue and what is the expected result after then.