Hi @MiaMaria , thank you for posting in the Q&A forum.
I have just tested in my SharePoint Online environment and everything works as expected.
Please check as following:
- Make sure you log in as a global admin account to rename the site via SharePoint admin center. You can switch to another global admin account to test again.
- Switch to another browser or clear the browser cache and test again.
- Try changing the site name in the site instead via Settings > Site information > Site name, or via classic Site Settings page > Title, description, and logo > Title. Log in as a Site Collection Administrator account to make the change and see if it works.
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