Hello @david frye
Welcome to the Q&A Forum!
Thank you for being cautious in this matter. In today’s fast-paced technological era, the ability to identify and double-check issues is extremely important, and I’m very glad to have supported you in doing this.
After discussing with my colleague, we have carefully double-checked this link for you and can confirm that it is legitimate.
When you click on the link, you will be prompted to set up the Microsoft Authenticator app. Once that is complete, you can also activate the product key through this link.
However, since you purchased this product key from a third-party provider, if you encounter any issues with the key, please kindly contact them to verify it for you.
For your reference: How to add your accounts to Microsoft Authenticator - Microsoft Support
Hope my information will be helpful for you.
Wishing you a pleasant day!
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