Hi @Charles Schmidt ,
Thank you for reaching out to Microsoft Q&A Forum.
I've been doing research about this, and it's indicated that Windows 11 E3 licensing activation required a Windows Pro device - which means the Windows Enterprise included in Microsoft 365 E3 license is not considered full edition to be directly download as fresh installation, it is considered to be an upgrade license from a base OS.
This also means you cannot download ISO file directly from Microsoft 365 Admin Portal.
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