Pivot table change data source
 

I have a pivot table that currently uses a range in another tab in the
worksheet. I would like to change the source to an external source, but it
will not allow me to do so.

I am using the newest excel in compatibility mode.
Under Options/ Pivot Table Tools/Change data source, it gives you 2 options.
The first option (currently checked) is "Select Table or Range". The
second option, Use external data source, is grayed out and will not let me
select this option.

Please help me figure out why I cannot change the source for my pivot table!
Thanks!