Removing Deny permission on Add and customize pages

In certain site collections, especially those created using Modern Team sites or Group sites, you might find a Deny permission on Add and customize pages. This permission rule prevents changes to site pages as a security measure. Unfortunately, it also means that you won't be able to customize your list forms using Ultimate Forms. You will be notified through a warning banner within the app if the permission is present within your site collection.

NOTE: If you have multi-factor authentication enabled in your environment, the script below will not work. Use the manual steps outlined in the blog article.

The permission rule can be easy removed using PowerShell. Download the script below here

Click on Windows icon and open or search SharePoint Online Management Shell

If you don't have SharePoint Online Management Shell installed, you can get it here: https://www.microsoft.com/en-us/download/details.aspx?id=35588
Type in the script file location
Execute and confirm:

Enter site URL and credentials:

You can also enter the script manually, follow the steps in this blog article.