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Office 365 Licence Activation Failure (Windows)

Pieter Engelbrecht
  • Updated

Office 365 Licence Activation Failure (Windows)

Section: Email & Microsoft 365 Tags: office365, licence, activation, windows, m365, outlook, unlicensed Source tickets: #25503 Confidence: High — full resolution path confirmed after Microsoft Support escalation

Symptom

One or more Office apps show a red banner: "Subscription expired" or "Unlicensed Product". Outlook may open in read-only mode or refuse to send/receive. The issue persists after signing out and back in.

Variants:

  • Office apps open but display "Product Activation Failed" at top
  • Outlook opens but cannot reply or send (incoming only)
  • Reinstalling Office via the portal does not resolve it

Root Cause

A stale or duplicate Office licence credential is cached in Windows Credential Manager. This causes Office to authenticate against the wrong account or an expired token — even after a fresh installation. The "My Office" COM add-in can also prevent clean licence assignment. The Microsoft Support and Recovery Assistant (SaRA) may report the issue as fixed but fail to clear the underlying token cache.

Prerequisites

  • Admin access to the Windows machine (local admin or via Remote Desktop)
  • The user's M365 email address and current password
  • Access to M365 Admin Centre to confirm the licence is assigned (admin.microsoft.com → Users → Active Users → [user] → Licences)
  • TeamViewer or RDP session

Remediation Steps

Step 1 — Confirm the licence is actually assigned in the tenant

Before touching the machine:

  • Log in to https://admin.microsoft.com
  • Go to Users → Active Users → select the user
  • Under Licences and apps, confirm a Microsoft 365 Business licence is assigned and ticked
  • If not assigned: assign it, wait 5 minutes, then test signing into Office on the machine
Expected result: If the licence was simply unassigned, Office activates after sign-in. Risk: None.

Step 2 — Remove all Office credentials from Windows Credential Manager

  • Open Control Panel → Credential Manager → Windows Credentials
  • Expand every entry containing "MicrosoftOffice", "Office365", "Office16", "MSOIDCacheV3", "Office_IdentityCache" — delete them all
  • Also check Generic Credentials for any Microsoft/Office entries — delete those too
  • Open Settings → Accounts → Access work or school — remove any school/work accounts listed
Expected result: No Office-related credentials remain. Proceed to Step 3 immediately. Risk: None — Office will simply prompt for sign-in again.

Step 3 — Uninstall the "My Office" add-in (if present)

  • Open Control Panel → Programs → Uninstall a Program
  • Look for "My Office" — if present, uninstall it
  • Reboot
This add-in can intercept licence checks and prevent clean activation. Expected result: Add-in removed. Proceed to reinstall. Risk: None.

Step 4 — Remove the Office product key via Command Prompt

  • Open Command Prompt as Administrator
  • Run:
cscript "C:\Program Files\Microsoft Office\Office16\ospp.vbs" /dstatus
Note any product keys listed (last 5 chars shown).
  • For each key listed, run:
cscript "C:\Program Files\Microsoft Office\Office16\ospp.vbs" /unpkey:<LAST5>
  • Repeat until /dstatus shows no keys
Expected result: Clean licence state. Office will require activation on next launch. Risk: None.

Step 5 — Uninstall and reinstall Office cleanly

  • Download and run the Microsoft Support and Recovery Assistant: https://aka.ms/SaRA-officeUninstallFromPC
  • Choose Uninstall Office — run the full removal
  • Reboot
  • Sign in to https://portal.office.com as the user
  • Go to Install apps → Microsoft 365 apps — download and install
  • On first launch of any Office app, sign in with the user's M365 credentials
Expected result: Office installs fresh, activates on sign-in, red banner gone. Risk: None to data — all email is on the server. Installation takes 20–40 minutes.

Verification

Open Outlook and each Office app. Go to File → Account — confirm "Product Information" shows the user's name and a green "Subscription Active" status. Send and receive a test email.

If This Fails

If activation still fails after a clean reinstall with all credentials cleared:

  • Create a new local Windows user account (admin) on the machine
  • Log in as that account and attempt to activate Office
  • If it activates under the new account: the original user profile is corrupt — migrate the user to a new profile
  • If it fails under the new account too: raise a ticket with Microsoft Support (admin.microsoft.com → Support → New service request), providing the Office install ID shown during activation

Related

  • Article: Outlook Password Prompts on Mac — separate issue, macOS-specific
  • Article: Office 365 Email Migration via MigrationWiz — for new tenant setups

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