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How to fix APIClient.dll was not found on Windows 10

Problems with DLL files result in obscure errors on Windows 10. These files are a part of the libraries installed on your system. They’re not stand-alone files that you can download again to fix whatever problem you’re having. Often, the DLL file that an error message says is missing is in fact present in the exact location it should be. It makes the problem all the more difficult to solve.

ApiCIient.dII was not found

The full error message that you see for the ApiClient.dll file not found is the following;

The code execution cannot proceed because Files\Common Files\Microsoft Shared\CIickToRun\ApiCIient.dII
was not found.

This is an error that users see when they try to open a Microsoft 365 app. You will only see it on Windows 10 and not on macOS. Here’s how you can fix it.

1. Re-register DLL file

If the DLL file is still present on your system, re-registering it will fix the problem.

  1. Open File Explorer.
  2. Navigate to the following location.
C:\Program Files\Common Files\microsoft shared\ClickToRun
  1. Check if the ApiClient.dll file is present.
  2. If the file is present, open Command Prompt with admin rights.
  3. Run the following command.
regsvr32 /u "C:\Program Files\Common Files\microsoft shared\ClickToRun\ApiClient.dll"
  1. Restart the system, and then open a Microsoft Office app.

2. Re-install Microsoft 365

If re-registring the DLL file doesn’t work, or the DLL file is not present in the location the error message mentions, your only option is to uninstall and re-install Microsoft Office.

  1. Open Control Panel.
  2. Go to Programs>Uninstall a program.
  3. Look for, and select Microsoft 365.
  4. Click the Uninstall button at the top and allow the apps to be uninstalled.
  5. Visit the Microsoft 365 page, and click Get Office.
  6. Sign in with the account you used to buy your Microsoft/Office 365 subscription.
  7. Download the app and install it.
  8. Open a Microsoft 365 app and it will open without showing the error.


There’s no one reason for why DLL files cause problems with apps. They may be corrupted for any number of reasons e.g., a forced shutdown, a BSOD, an app crash, a bad app update, or a library update that did not install correctly. One thing we strongly discourage you from doing is finding these DLL files online and downloading them to your system. The DLL files may be malicious. They are never distributed by any official developer. Instead, you will find them on various file and software repositories and there is no telling whether or not they’re safe or if they will fix whatever problem you’re having. It is always better to uninstall and reinstall libraries or apps to fix problems with DLL files.

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