Hey Cameron -
Since you're using a Data Server based data source, the option is disabled. If you choose to Create Local Copy, you'll be able to refresh the copy.
Why is this so? I don't know for sure, but I suspect our designers think that once a data source has been published to Data Server, it should be a Server Administrator who is responsible for the care and feeding of that data source (not a Desktop user consuming it).
Hope this helps a little?
Thanks Russell for that advice. Where is the Create Local Copy function accessed?
My apologies, I didn't look closely at the first post--I just read your post about where to find Create Local Copy. This option is only available if you're connect to a Tableau Data Server connection, but from the above screenshot I can see that you're connected to an extract file, not the former. In order for the 'Extract' option to be available--an extract of the extract will need to be taken--since the you are connected to the extract directly. So, after creating another extract (by clicking Extract Data...) the other options will appear.
Hope this helps!