Good Morning Kayli,
Could you post a sample workbook that exhibits the problem so we can take a look at it? Or at least a screen shot of the View you are working on?
The only thing I can think of blindly is to double check that you've actually placed a dimension on the 'Label' tile. A greyed out text box would be expected behaviour if there is nothing currently on the Label tile in the marks card.
Tableau Online Deployment Advisor