We can't make this change because the selection is locked

The error message "We can't make this change because the selection is locked" typically indicates that the document is protected or that editing is restricted. To resolve this issue, you can try the following steps:

1. Check Document Protection: Go to the Review tab and see if the document is protected. If it is, you may need to unprotect it by selecting Restrict Editing and then clicking on Stop Protection.
2. Check for Read-Only Status: Ensure that the document is not opened in read-only mode. You can check this by looking at the title bar of the window. If it is read-only, try saving a copy of the document and then editing the copy.
3. Check Permissions: If the document is shared, ensure that you have the necessary permissions to edit it.

Regarding the "Product activation failed" error when trying to create a new Word document, this usually indicates that your Microsoft 365 Apps are not activated. Here are some steps to troubleshoot this issue:

1. Sign Out and Sign Back In: Open a Microsoft 365 app, select your name or profile picture at the top, sign out, and then sign back in using your work or school account.
2. Run the Microsoft 365 Activation Troubleshooter: You can use the troubleshooter to help resolve activation issues. Open the Get Help app and follow the instructions to run the troubleshooter.
3. Check Your License: Ensure that your Microsoft 365 subscription is active and that you are using the correct account associated with your subscription.
4. Update Microsoft 365: Make sure that your Microsoft 365 apps are up to date. Open an app, go to File > Account, and select Update Options > Update Now.

If these steps do not resolve the issues, you may need to contact your Microsoft 365 admin or support for further assistance.

Hello, thank you for reaching out to Microsoft Q&A.

You're receiving this error because your Office Product is not activated.

May I please confirm whether you're using a trial version of Office that has expired, or if your subscription has not been renewed?

Open any Office app such as Word, then go to File > Account to reactivate it. If you're prompted to resubscribe, you will need to purchase a subscription and then activate Office.

If you’re still having issues, please let me know the following:

1. Which edition of Office is installed on your device or which edition you have a license for? For example, Office Home 2024, Microsoft 365 Personal, etc.
2. Do you see your license listed under your Microsoft account on the Services & subscriptions page?

You can check here: https://account.microsoft.com/services