You're installing an Office Add-in that runs on Windows, Macs, and the web versions of Office applications. An older Windows-only version of the add-in is already installed on your computer.
Running multiple add-ins that register the same commands, ribbon controls, or custom functions can cause conflicts, so you must disable either the old or new version. The publisher of the add-in recommends that you disable the older version. The dialog asks for your choice of which version to disable.
If you select Yes, the new version of the add-in is installed on all platforms that support Office, including Windows, Mac, and Office on the web. For Outlook add-ins, the add-in is installed on classic Outlook for Windows, new Outlook Windows, as well as Mac and Outlook on the web. The old Windows-only version is disabled.
If you select No, the following things happen:
- The new version of the add-in is installed only on Mac and Office on the web. For Outlook add-ins, the add-in is installed on Mac, Office on the web, and new Outlook for Windows.
- The old version of the add-in continues to work on Windows. The new version is disabled on Windows (and on classic Outlook on Windows).
You can change your decision later by using the following steps:
- In the ribbon of the Office application where the add-in is installed, go to File > Options > Add‑ins.
- Select a type in the Manage drop down list, and then select Go.
- Use the dialog that opens to enable or disable an add-in. For more information, see Add or remove add-ins in Excel. (Although the title refers to Excel, the guidance applies to all Office applications.)
For further help
- Review your organization's add‑in policy in the Microsoft 365 admin center.
- Contact your IT support or the add‑in publisher with screenshots and log files.