I have a SharePoint Online environment as
Now I am trying to add custom JS codes to the site page in the above specified site. Whenever I try to add the code on top level root site it always throws error:
Access denied. You do not have permission to perform this action or access this resource.
FYI: I am the owner of the tenant.
Also when I tried opening top level root site using SPD, there also I got the same error.
So, I want to know whether its possible to add some custom codes on the top level root site collection?
If its possible then how we can achieve this?