Hello,
This is a known issue and you can't activate it because it became Enterprise edition somehow.
You need to downgrade it to Pro edition and then it should be automatically activated.
Refer this fix (works with Windows 11 as well):
https://www.kapilarya.com/fix-upgrade-from-windows-10-home-to-pro-results-in-enterprise-edition
Hope this helps!
Note: Included link in this reply refers to blog post by a trusted Microsoft MVP.