If you get this error

System.InvalidCastException: Unable to cast COM object of type ‘System.__ComObject’ to interface type ‘Microsoft.Office.Interop.Outlook._AppointmentItem’. This operation failed because the QueryInterface call on the COM component for the interface with IID ‘{00063033-0000-0000-C000-000000000046}’ failed due to the following error: Library not registered. (Exception from HRESULT: 0x8002801D (TYPE_E_LIBNOTREGISTERED)).
Source: mscorlib
TargetSite: IntPtr GetCOMIPFromRCW(System.Object, IntPtr, IntPtr ByRef, Boolean ByRef)
HResult: -2147467262
StackTrace: at System.StubHelpers.StubHelpers.GetCOMIPFromRCW(Object objSrc, IntPtr pCPCMD, IntPtr& ppTarget, Boolean& pfNeedsRelease)
at Microsoft.Office.Interop.Outlook._AppointmentItem.get_EntryID()
at EIOBoard_Outlook_Addin_2010.EBRibbon.bwLoader_DoWork(Object sender, DoWorkEventArgs e)

or something similar when using the Outlook add-in-

Do the following:

  1. Using the Registry, navigate to: HKEY_CLASSES_ROOT\TypeLib{00062FFF-0000-0000-C000-000000000046}
  2. Delete the version keys (e.g. 9.5) for any version of Outlook that is not installed on your system based on the version table provided below. For example, if you are not using Outlook 2013 then remove the “9.5” entry. If you are not using Outlook 2010 then remove the the “9.4” entry. DO NOT DELETE the entry for the version that was configured in Step #1

Outlook 2007 ==> 9.3

Outlook 2010 ==> 9.4

Outlook 2013 ==> 9.5



This error is usually caused when a later version of Outlook has been installed and then the user reverted back to an older one. It can also be caused when a system is upgraded from Windows 7 or 8 to 8 or 10

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