Formula between Worksheets

Hi,
I am having a problem using (Sheet2!D4) formula in a worksheet. I'm getting an Update Message, and the cell I am putting the formula shows # REF , and not the result of the formula.

I did not create this workbook or the worksheets , but received the information by e-mail from my client. Each worksheet within the workbook was named with a number and name, e.g, "5409 Smith"

Any suggestions.

Thanks, PJG