When we trying open the Office 365 SharePoint site (" https://domain.sharepoint.com") in SharePoint Designer 2013, which giving the error "You do not have permission to open this website in SharePoint Designer".
In error details 403 forbidden 403 forbidden 403 forbidden
In error details 403 forbidden 403 forbidden 403 forbidden
Solution:
1) Check the current account in your SharePoint Designer is the Office 365 account
Once again renter the user name and password what you have using in Office 365
2) Go to the Office 365 Active user page https://portal.office.com/Admin/Default.aspx#ActiveUsersPage and make sure that the user account which one you are using in sharepoint designer should licence assigned.
3) recommend to check your permission in that web site, ensure you have permission to open that web site in SharePoint Designer.
Go to Site Permissions > Permission Level in ribbon > click the permission you belongs to > Ensure Use Remote Interfaces is selected.
Go to Central Administration > Application Management > User Permissions for Web Application > make sure the option to Add and Customize Pages is checked/enabled.
PLEASE give your feedback..