Access denied in office 365 / SharePoint Online

•  Login your Office 365 account.
• Go to the SharePoint admin center.
• Select Settings.
• Under Custom Script choose:

• Prevent users from running custom script on personal sites or Allow users to run custom script on personal sites.
• Prevent users from running custom script on user created sites or Allow users to run custom script on self-service created sites.

var tenant = new Tenant(ctx);
    var SiteProp = tenant.GetSitePropertiesByUrl(http://devprasad007-admin.sharepoint.com, true);
    ctx.Load(SiteProp);
    ctx.ExecuteQuery();

    SiteProp.DenyAddAndCustomizePages = DenyAddAndCustomizePagesStatus.Disabled;
    var result = SiteProp.Update();
    ctx.Load(result);
    ctx.ExecuteQuery();
    while (!result.IsComplete)
    {
        Thread.Sleep(result.PollingInterval);
        ctx.Load(result);
        ctx.ExecuteQuery(); 

    }