Dogknees was the first to mention that the calculation method might be set to Manual - and that is the problem, but as bill.kuunders mentioned, it gets worse.This isn't a case of the calculation switch being flipped for a single workbook.
When you set the cell formatting to “Text”, Excel treats the formula as text and shows it instead of evaluating it. To fix this error, just select the cell, set its formatting to “General”. (Alternatively you can press F2 and then Enter after setting format to General). ) I'm glad Nrobinson5 brought up this possibility though.It's a great place to start troubleshooting and could easily have been the problem.I can only assume that somehow the file had become corrupted.
I also have had this problem with a very large spreadsheet that just stopped updating itself over the weekend, but having checked the above solutions, setting were already set to automatic, and sheet is too big to rebuild, so I was at a loss.Specifically, the first formula worked fine, but when we copied it, the formula returned the result of the first formula. In the example sheet, I entered a SUM() function to total each salesperson's commission (row 8) and bonus (row9).Nrobinson5 suggested that the formula uses absolute references: instead of =SUM(B8: B9), I entered formula =SUM($B:$B). So instead lets roll up our sleeves and find out the reason for this mishap.You may have set the cell formatting to “Text” and then typed the formula in it. Three attempts later and it was still adamant it wanted to be "Manual" and nothing else.