why am I being asked to activate with a product key

That message usually means Microsoft Word (or Office) on your computer isn't activated. When Word is installed without a valid license, it lets you open and view documents, but you can't edit, save, or create new ones until you activate it.

The potential reasons include:

• Trial version expired – If Word came preinstalled (often as a trial), once the trial runs out, you'll need a valid license.
• No license tied to your account – If you never signed in with a Microsoft account that has an Office subscription or purchased license, Word will stay in "unlicensed" mode.
• Product key needed – If you bought Office as a one-time purchase, you'll need to enter the product key that came with it.
• Subscription lapsed – If you had Microsoft 365 but stopped paying, it reverts to view-only mode.

To fix this:

1. Sign in to Word with the Microsoft account you used to buy Microsoft 365 or Office.
2. If you bought a product key card, enter the 25-digit code at setup.office.com.
3. If you don't have a license, you'll need to purchase one or switch to a free alternative (e.g., Word Online via your Microsoft account)

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hth

Marcin