[excel] Excel is not updating cells, options > formula > workbook calculation set to automatic

I had this happen in a worksheet today. Neither F9 nor turning on Iterative Calculation made the cells in question update, but double-clicking the cell and pressing Enter did. I searched the Excel Help and found this in the help article titled Change formula recalculation, iteration, or precision:

CtrlAltF9:
Recalculate all formulas in all open workbooks, regardless of whether they have changed since the last recalculation.

CtrlShiftAltF9:
Check dependent formulas, and then recalculate all formulas in all open workbooks, regardless of whether they have changed since the last recalculation.

So I tried CtrlShiftAltF9, and sure enough, all of my non-recalculating formulas finally recalculated!