reactivation of Office 2021 professional plus

Question

reactivation of Office 2021 professional plus

Joe Fusco 25

Office2021 has become deactivated on my computer. It asks me for a product key. This was preinstalled on my computer by a third party. The third party has since passed away. I have the last 5 digits only. I have an invoice that he purchased Office 2021 but k=not where it was purchased from. Is it possible to reactivate?

Joe Fusco 25 Reputation points

2026-10-06T16:13:23.32+00:00

I have a product ID number

Answer accepted by question author

Jayden-P 3,375 Independent Advisor

Hi @Joe Fusco

If Office 2021 was activated using a retail product key, the full 25-character key would be required for reactivation. The last five characters alone cannot be used to recover the full key.

However, if the license was previously associated with a Microsoft account, signing in with that account may automatically reactivate Office. I recommend checking the Microsoft account used during the original setup and reviewing the purchase invoice for any reseller or order details that could help locate the original license information.

You can try the following:

Open any Office app and go to File > Account.
Check which Microsoft account (if any) is associated with the Office installation.
Sign in to https://account.microsoft.com/services with any Microsoft accounts you may have used previously and see if Office 2021 appears there.

If the original third party never provided the key and the license is not associated with a Microsoft account that you can access, it typically cannot reconstruct a lost Office 2021 product key from only the last 5 characters.

Joe Fusco 25 Reputation points

2026-10-06T16:15:44.0933333+00:00

I have a product ID number
Jayden-P 3,375 Reputation points Independent Advisor

2026-10-06T16:15:47.1166667+00:00
A Product ID unfortunately cannot be used to reactivate Office or retrieve the original 25-character product key. The Product ID only identifies the installed Office product. To reactivate Office 2021, you would typically need either:

The original 25-character product key, or

Access to the Microsoft account that the Office license was associated with.
Joe Fusco 25 Reputation points

2026-10-06T16:17:30.01+00:00

Ok, thank you
Jayden-P 3,375 Reputation points Independent Advisor

2026-10-06T16:19:26.8933333+00:00

You're welcome, hope you're having a good day.

1 additional answer

Your answer

Joe Fusco 25 Reputation points

2026-10-06T16:13:23.32+00:00

I have a product ID number
Joe Fusco 25 Reputation points

2026-10-06T16:15:44.0933333+00:00

I have a product ID number
Jayden-P 3,375 Reputation points Independent Advisor

2026-10-06T16:15:47.1166667+00:00

A Product ID unfortunately cannot be used to reactivate Office or retrieve the original 25-character product key. The Product ID only identifies the installed Office product. To reactivate Office 2021, you would typically need either:

The original 25-character product key, or

Access to the Microsoft account that the Office license was associated with.
Joe Fusco 25 Reputation points

2026-10-06T16:17:30.01+00:00

Ok, thank you
Jayden-P 3,375 Reputation points Independent Advisor

2026-10-06T16:19:26.8933333+00:00

You're welcome, hope you're having a good day.

Answer 1

Old observer 245 Volunteer Moderator

Office Professional Plus can be preinstalled only by order of an organization that has the appropriate Office license. So, please contact your company's system administrator.

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