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# How to fix: "Unable to cast COM object of type System.__ComObject..."

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  width: width
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<Info>
  This guide is provided by Conductor, the service that powers the QuickBooks
  Desktop integration for many business tools, including the one that sent you
  here.
</Info>

If a Conductor error message directed you to this page, it's because we encountered the following error when attempting to connect to QuickBooks Desktop on your computer:

```
Unable to cast COM object of type 'System.__ComObject' to interface type
'Interop.QBXMLRP2.RequestProcessor2'. This operation failed because the
QueryInterface call on the COM component for the interface with IID
'{8DB91B17-D5A2-41DB-80A7-CC6F1E449A05}' failed due to the following error:
No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)).
```

## Solution

Complete the following steps to re-register the QuickBooks Desktop components to resolve this issue:

<Steps>
  <Step title="Close QuickBooks Desktop">
    Ensure QuickBooks Desktop is completely closed.
  </Step>

  <Step title="Open Command Prompt (cmd.exe) as an administrator">
    Using Windows search (usually located in the bottom-left corner of your screen), type "**cmd**", right-click on the "**Command Prompt**" result, and select "**Run as administrator**".

    <Image src="/images/help/connection-errors/unable-to-cast-com-object/run-command-prompt-as-admin.jpg" alt="Run Command Prompt as administrator" width={550} />
  </Step>

  <Step title="Run the command to re-register QuickBooks components">
    Copy the **entire** command below, then paste it into the PowerShell window and press Enter.

    ```shell theme={"system"}
    "%windir%\SysWOW64\regsvr32.exe" "C:\Program Files (x86)\Common Files\Intuit\QuickBooks\QBXMLRP2.dll"
    ```

    <Image src="/images/help/connection-errors/unable-to-cast-com-object/command-prompt-reregister.jpg" alt="Re-register QuickBooks components via Command Prompt" />

    If the command was successful, you will see a success message resembling the screenshot below.

    <Image src="/images/help/connection-errors/unable-to-cast-com-object/command-prompt-reregister-success.jpg" alt="Re-register QuickBooks components via Command Prompt" />
  </Step>

  <Step title="Restart your computer">
    If the command was successful, restart your computer to ensure the changes take effect. After restarting, try connecting to QuickBooks Desktop again.
  </Step>
</Steps>

These steps should resolve the COM object casting error by properly registering the QuickBooks components with your system.