Excel workbook is not activated when you run a macro that calls the Workbook.Activate method
To work around this issue, set the ScreenUpdating property to True before you call the Activate method. You can set it back to False, as needed, after the Activate method runs, as in the following code example:
Application.ScreenUpdating = True Workbooks(1).Activate Application.ScreenUpdating = False
This code may introduce a screen flash and may alter the content that's displayed for Excel while the macro runs.
In Excel 2013, the single document interface (SDI) feature was introduced. Excel 2013 workbooks are now top-level windows in Windows. In this configuration, Windows handles the activation of windows instead of Excel managing the child windows as it does in earlier versions of the program.
In the scenario that's described in the "Symptoms" section, Excel requests that Windows activate the workbook, but the workbook's window does not meet the Windows activation requirements.