When I type in the VLookup formula and hit enter, the cell will not display
the result - it displays the formula. Then, when I copy it to the cells
below, none of the cell references change.

Here is the formula: =VLOOKUP(C2,Sheet1!A:B,2,false)

I made this same formula in an older file and it worked fine. Why won't it
work in this new spreadsheet? I think something happened to the settings,
but I don't know where to go to fix it.