Out of the box, that page type does not exist, was your site upgraded from version 12?
Are you a global administrator or have access to edit those field properties?
Is that page type created as a page type with no field representation? You can verify this on the General tab of the page type by looking for a Table name field with a value. If there is no table name field and value, then it has no database representation and was created without fields. It would then need to be recreated as a page type with fields if you wanted to add fields to it.
