I have a number of spreadsheets written with VBA code in the background that that rely on iterative calculations until a solution is found. These worked fine up until around the 11th of February 2025. Since then the Worksheets("Sheet1").UsedRange.Calculate has not been working. I have to set the workbook up to Application.Calculation = xlManual, otherwise some of my calculations can become unstable. I have then been cascading the calculations across the sheets in a specific order to allow the data to flow through.

In simple terms my problem is that if I open a new workbook and for example set cell A1 to =B1 and cell B1 to =A1+1. This should increment the values every time I recalculate the sheet. Indeed if I F9 it does. However, when the workbook is set to: Application.Calculation = xlManual, though F9 still works Worksheets("Sheet1").UsedRange.Calculate does not. Please see my test code below including comments.

Sub TestCalculate()
Worksheets("Sheet1").UsedRange.Calculate 'Now only works when Automatic Calculations are enabled.`  
'Application.Calculate 'Works fine with or without Automatic Calculation enabled but calculates the whole workbook which is not what I need.`
End Sub

I feel like this maybe linked to an Office 365 update as I cannot understand why else it would stop working but am reluctant to roll back the version and have this problem reappear later. Any help would be greatly appreciated. Many Thanks