Selected Personal account accidentally for Microsoft 365 business and now the rest of the 4 people cannot use their outlook anymore. How to fix this ?

The email address is now associated with both a personal Microsoft account and a work/school (business) account, and Outlook/Office is trying to use the personal account, which cannot activate Microsoft 365 Apps for business.

Use these steps to recover:

1. Make sure Outlook and all Office apps are closed on all affected PCs.
2. On each affected PC, sign out of Office completely and sign back in with the work or school account:
   1. Open any Microsoft 365 app (for example, Word).
   2. Go to File > Account.
   3. Under User Information, select the account name and choose Sign out for all listed accounts.
   4. Close the app, then reopen it.
   5. Go back to File > Account and select Sign in.
   6. When prompted with “It looks like this email is used with more than one account…”, choose the work or school account (the “IT group”/organization option), not the personal account.
   7. Confirm that under Product Information the subscription shows as a business/organization license and that the signed-in account is the work or school account.
3. If activation still fails on any device:
   1. In the Microsoft 365 Admin Center, check that the correct user accounts have licenses assigned:
      • Go to Users > Active users.
      • Select each affected user.
      • Choose Licenses and Apps.
      • Ensure the appropriate Microsoft 365 license is checked, then select Save changes.
      • If already assigned, uncheck the license, Save changes, then re-check and Save changes again to refresh the assignment.
   2. On the affected PC, run the Microsoft 365 sign-in troubleshooter from Get Help to automatically fix common sign-in and activation issues: see the Microsoft 365 sign-in troubleshooter referenced in the context.
4. If the sign-in dialog keeps preferring the personal account:
   1. In Windows Settings > Accounts > Email & accounts and Access work or school, remove any personal Microsoft accounts that use the same email address.
   2. Sign out of all browsers and clear cached credentials, then try signing in again with the work or school account when prompted.
5. If the email address truly needs to be used only as a business identity, consider renaming the personal Microsoft account so that the conflict no longer occurs:
   • Go to the Manage how you sign in section of the personal Microsoft account.
   • Add a new alias (email address) and set it as Make primary.
   • This leaves the work/school identity as the primary use of the original email address and reduces future “Which account do you want to use?” prompts.

If, after these steps, Outlook for Microsoft 365 still refuses the work/school account on any machine, use the Outlook/Office sign-in and activation troubleshooters referenced below to automatically diagnose and repair profile and license issues.

References:

• Which account do you want to use?
• What's the difference between a Microsoft account and a work or school account?
• Microsoft 365 Apps activation error: "The products we found in your account can't be used to activate"
• Microsoft 365 apps activation error "Another account from your organization is already signed in on this computer"
• "Sorry, another account from your organization is already signed in on this computer" in Office 2013
• Fix Outlook account problems in Office 365 for business
• Accept an email invitation to a Microsoft 365 for business subscription organization using an Outlook, Yahoo, Gmail, or other account (User)