Checking web.config for the current v7 site I was working on, the umbracoConfiguration / settings section is of type Umbraco.Core.Configuration.UmbracoSettings.UmbracoSettingsSection .
Another thing you are doing wrong is to use as IUmbracoSettingsSection . Since this means that if the failure fails, you return a null object, not an exception, indicating that the throw was unsuccessful - it fails. Better to do:
var umbracoSettings = (IUmbracoSettingsSection)ConfigurationManager.GetSection("umbracoConfiguration/settings");
As already mentioned, I think your base type is wrong, and you really should use:
var umbracoSettings = (Umbraco.Core.Configuration.UmbracoSettings.UmbracoSettingsSection)ConfigurationManager.GetSection("umbracoConfiguration/settings");
This should make the section suitable for you.
source share