How to prevent Office 365 overiding Office 2019?

Rose 0 Reputation points
2026-10-08T15:03:03.5433333+00:00

I am the IT administrator for a group with several computers, each used by multiple users every day. We have individual perpetual licenses of Office 2019 installed on each PC's. The computers are not hooked up to the internet for long periods of time. It is not practical for us to use Microsoft 365. We uninstalled Microsoft 365 before installing 2019, so that is the only version we have. We want to use Office 2019 at least until the next release of the perpetual version of Office after Office 2024. We are choosing to go without support until we upgrade.

We have a few users who are taking college classes and have a Microsoft 365 email/account for school. Sometimes, not every time, when logging into Microsoft 365 in a web browser not the app or Outlook, it causes Office 2019 to switch over to Microsoft 365. Sometimes it does this on its own. I assume this should not cause it, but it does. Most times, we need to uninstall both versions of Office and reinstall Office 2019. Sometimes we get lucky and are able to resolve the issue of having Office 365 with a simpler solution. The number of times we need to do this has been increasing. The time to try different solutions until one works has been increasing as well.

I have looked at other questions from people in similar situations, and the answers deal with how to fix this when it happens. Is there a way to prevent this from happening? Is there a setting in the Group Policy Editor or somewhere else to stop this?

Microsoft 365 and Office | Install, redeem, activate | Other | Windows
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  1. Rukshan edirisinghe 1,645 Reputation points
    2026-10-14T05:01:59.9566667+00:00

    Hi @Rose

    What usually triggers this is a student signing in to the Office 2019 apps with their school account. That account carries a Microsoft 365 license, and Office can detect it and switch the install over. Signing in on the web shouldn't do it on its own, but Office can pick up that account from Windows or the browser session and prompt for it.

    The way to prevent it is to stop school/work accounts from signing in to the Office desktop apps. There's a policy for exactly that:

    1. On one test PC, open the Group Policy Editor with the Office ADMX templates installed and go to User Configuration > Administrative Templates > Microsoft Office 2016 > Miscellaneous. (Office 2019 uses the 2016 templates.)
    2. Open Block signing into Office, set it to Enabled, and choose Microsoft account only. That still allows a personal Microsoft account (which retail Office 2019 may need for activation) but blocks organization accounts like the school ones.
    3. If you'd rather set it directly, it's the SignInOptions DWORD under HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\SignIn. Value 1 = Microsoft account only, 4 = no sign-in at all. (The reference below was written for Office 2013, but the same setting applies under the 16.0 key.)
    4. Since it's a per-user setting and the PCs are shared, apply it to every user profile, for example through local Group Policy for all users or a logon script.
    5. Test with a student account for a few days before rolling it out everywhere.

    The students can still use their school Microsoft 365 in the browser. They just can't attach it to the installed Office apps.

    Is Office 2019 on these PCs a retail version tied to a Microsoft account, or a volume license version?

    If this resolved your issue, please consider accepting it as the answer. If Office still switches after the policy is applied, let me know and I'll be happy to keep helping.

    Reference:

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