Error: "We can't start this app" when you install an Office add-in

Symptoms

When you try to install an add-in from the Office Store, you receive the following error message:

We can't start this app because it isn't set up properly.

Cause

This issue occurs because of incorrect information in the Windows registry.

Resolution

Warning

Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall the operating system. Microsoft can't guarantee that these problems can be solved. Modify the registry at your own risk.

To resolve this problem, follow these steps:

1. Exit any open Office applications.

2. Start Registry Editor. To do this, press the Windows key+R to open the Run window, type regedit, and then press Enter.

3. Locate and select the following subkey:

   HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\WEF\Providers

4. For each subkey under Providers, follow these steps:

   1. Select the subkey, and check the value data for its UniqueId entry.

   2. If the value of UniqueId is one of the following values, delete the subkey:

      • <GUID>_ADAL: <GUID> is a random set of numbers and letters, such as 3a975b5d-ad3e-4e3d-84b0-a7e6776ba6a6.
      • Anonymous

   For example, the subkey under HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\WEF\Providers is KpwDSnL9jumf9ZJTx_XF_Q==, and its UniqueId value is 3a975b5d-ad3e-4e3d-84b0-a7e6776ba6a6_ADAL. In this case, delete the KpwDSnL9jumf9ZJTx_XF_Q== subkey.

5. Exit Registry Editor.

6. Open File Explorer, and delete the following folder:

   C:\Users\<your username>\AppData\Local\Microsoft\Office\16.0\Wef

   If you can't locate the folder, press the Windows key+R to open the Run window, type the following path, and then select OK:

   %localappdata%\microsoft\office\16.0\Wef