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Last Updated: April 28, 2021


After installing the April 2021 security update to Microsoft Office, some automation add-ins for Excel may not load and you could see a “Cannot run the macro” error message.


To work around this issue, you will need to make a change in the registry. 

Important: The following steps show you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Please make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, go to How to back up and restore the registry in Windows.

  1. Identify the name of the automation add-in that fails to load. In later steps, we will refer to this name as <ProgID>.  To verify the add-in name, view your list of add-ins in the Excel Add-in Manager.

    1. From an open Excel sheet, select File, choose Options, and then choose the Add-Ins category.

    2. In the Manage box, select Excel Add-ins, and then choose Go. This will display the add-ins manager with your list of available add-ins.

  2. From the Start menu, type regedit.exe in the search box, and then press Enter.
    If you are prompted for an administrator password or for confirmation, type the password or provide confirmation.

  3. In Registry Editor, navigate to: HKEY_CLASSES_ROOT\<ProgID>

  4. If a sub-key CurVer exists, retrieve the (default) value from the sub-key CurVer. Treat this as your new <ProgID> and repeat step 3. If a sub-key CurVer does not exist, continue to step 5.

  5. Retrieve the (default) value from the sub-key CLSID - we will refer to this as <CLSID> in later steps.

  6. Navigate in the registry to: HKEY_CLASSES_ROOT\<CLSID>\InprocServer32

  7. If the (default) value is mscoree.dll, change it to C:\Windows\System32\mscoree.dll

  8. Close Registry Editor

  9. Close all Excel instances and then reopen Excel. Try the add-in again.

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See Also

Fixes or workarounds for recent issues in Excel for Windows

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