Why this happens:
You may be signed into Office using an account tied to Microsoft 365, which is subscription-based
Office may default to showing a trial/expired subscription screen when it doesn’t detect the correct activation method
Your PC may still be pulling activation details from an older Office install
How to fix it
Confirm what Office version is installed
Go to Control Panel > Programs (or Settings > Apps) and check the exact Office name listed (for example, Office Professional Plus 2021).
If you see “Microsoft 365 Apps”, that’s not the correct edition for a one-time purchase installation.
Remove the incorrect Office version
Uninstall the Microsoft 365 / trial installation and restart your PC afterward.
If you have an automatic Office installer from your delivery instructions, you can use its built-in uninstall option to remove older Office versions first (recommended).
Install the correct Office edition
Download and run the installer that matches your purchase (using the link provided in your order email/instructions).
During installation, avoid signing in with a Microsoft 365 subscription account if prompted.
Enter your product key
Open Word or Excel, then go to Account > Change Product Key and enter the key you received.
Once completed, the “subscription expired” message should disappear.