Excel cannot convert the PivotTable to formulas.
One or more filtered fields are not completely visible. To convert a cell to a formula, all items that are used in the formula must be visible.
To make the filtered fields completely visible, do one or more of the following:
Expand the entire field for all fields in levels above the filtered fields.
If grand totals are displayed, display the subtotals as well.
Then, try to convert the PivotTable cells to worksheet formulas again.