When I use the workbooks.range.formular1c1 object in VBA, the formula's do
not calculate and instead show #NAME? as the value. I can edit each cell and
then press ENTER to get the values to update, but is there a way to get the
values to show as soon as the code completes?

The VBA statement is

worksheet.Range("B2").FormulaR1C1 = "=sumif(sheet1!A:A,rc[-1],sheet1!D:D)"

to sum all the rows in column D of sheet1 where the column A row = the value
in cell A2 on the current sheet. There is no problem with the formula
itself, since just selecting the cell and pressing F2 and ENTER updates the
value.