Hello,
Thank you for posting in Microsoft Community forum.
Based on the description, I understand your question is related to Microsoft Windows 10/11 Enterprise A3 licenses.
Microsoft 365 A3 is designed for educational institutions. The Microsoft 365 A3 subscription does not support subscription activation from Windows Pro to Enterprise. This feature is available only with Windows Enterprise E3 or E5 licenses.
The subscription activation feature enables a "step-up" from Windows Pro edition to Enterprise edition or from Windows Pro Education edition to Education edition. This feature can be used with a subscription to Windows Enterprise E3 or E5 licenses.
Windows subscription activation | Microsoft Learn
Have a nice day.
Best Regards,
Molly