Hi Guys, I have been recently working on an issue regarding being unable to enable Content Editor on a certain SharePoint online site within a customer’s environment. Firstly we had a thought that the user who reported the issue might not have the correct permissions to use or enable the Content editor on the site but, after checking this we quickly found that the user had full control over the problematic site.
After some quick research we found a handy little command that you can use within the SharePoint Online PowerShell Module. Here is the command we used: Set-SPOsite <SiteURL> -DenyAddAndCustomizePages 0
Once you have found the site problematic site URL you can go ahead and set the DenyAddAndCustomizePages to 0, refresh the page and there you have it Content editor has now been enabled on the site. Hope this helps! Thanks for reading!