Title pretty much says it all.  Anyone else run into this with Office/Excel 2010?  I have various users from different departments reporting that formula's don't work until they turn Calculate back to automatic from manual..  Why was it on Manual?  Nobody knows.....

Hi ATyler,

As far as I know, if you open an Excel file and set the calculation mode to Automatic, then open another Excel file that has been saved in Manual mode, it will NOT change to Automatic mode. Conversely, if you open an Excel file that has been saved in Manual mode, then open another Excel file saved in Automatic mode, it will CHANGE to Manual mode.

You can refer to this thread and read the answer of MVP Charles, he said >>if people are not careful Manual Calc mode spreads like a virus.<<

https://social.msdn.microsoft.com/Forums/sharepoint/en-US/a98acbee-81c9-4a42-9e19-5f0f7fc1d92b/excel-arbitrarily-changing-calculation-to-manual?forum=exceldev

This might be the reason of your issue.

As a workaround, you can create a Personal.xlsb on: UserName\AppData\Roaming\microsoft\excel\Xlstart folder

When you saved the file "Personal.xlsb" in the Xlstart Folder, open an Excel file and press ALT+F11

On the left side, open the VBAProject(Personal.xlsb) and double click on ThisWorkbook and paste this code:

Private Sub Workbook_Open()
     Application.Calculation = xlCalculationAutomatic
 End Sub

Then save it and restart Excel.

Please try this workaround and let me know if it works for you, I'm glad to help and follow up your reply.

Regards,

Emi Zhang
TechNet Community Su