Hi Brian Albright,
The issue isn't with downloading Windows 11 Pro itself, as the installation media is freely available from Microsoft; the product key is solely for activation. Your purchased key is a generic installation key used by the media creation tools and is not your unique license. Your actual license is digitally tied to your Microsoft account or hardware once activated.
To download the correct installation media, go directly to the official Microsoft website. Use the Media Creation Tool (MediaCreationToolW11.exe) for the most reliable process. Run this tool on a working Windows PC, select "Create installation media for another PC," choose Windows 11 Pro, language, and edition (Pro), and create either an ISO file or a bootable USB drive. Do not use the "Installation Assistant" if you are installing on a new or formatted drive, as that tool is designed for in-place upgrades on an already running system.
If you are attempting to download an ISO directly, ensure you select "Windows 11 (multi-edition ISO)" and choose "Pro" during setup. Your purchased product key will be entered after installation, under Settings > System > Activation. If you encounter a "Windows cannot be installed" error, verify your PC meets the TPM 2.0 and Secure Boot requirements. Should the activation fail post-installation, contact Microsoft support with your proof of purchase to bind the correct digital license to your account.
I hope you've found something useful here. If it helps you get more insight into the issue, it's appreciated to ACCEPT ANSWER then. Should you have more questions, feel free to leave a message. Have a nice day!
VP