Combo Box Empty on Preview

Hello,

I have a combo box that has the following labels: Avg Cost, Total Days, Total Cost.

The labels are in columns in a spreadsheet going across. Not in rows...

So my label range is A1:A3...

When I look at the combo box on the design all the labels are populated in the list.

But when I "preview" the combo box it shows up totally empty...

Can someone please help?