Why are you seeing an error?
In December Google updated their structured data testing tool to include validation for the new AMP features. As a result, you will see an error in the structured data testing tool, don't worry. The structured data you have from SchemaApp is working, Google is just getting excited and ready for AMP. The AMP feature is planned for implementation in search results in early 2016 even though their testing tool is showing errors for it. The error looks like this:
What is AMP?
Acclererated Mobile Pages (AMP) is a project supported by Google and Twitter to improve the user experience for people on mobile pages. Google announced AMP in October on their blog and says that it "aims to dramatically improve the performance of the mobile web. We want webpages with rich content like video, animations and graphics to work alongside smart ads, and to load instantaneously. "
To fix the Image property you must choose a Featured Image for your Page or Post. Without which, the plugin doesn't know which photo best represents the content. The plugin will use this to insert the ImageObject with its width and height properties.
To fix the Publisher properties we have added the ability for you to add your publisher settings in the Wordpress Plugin. Go to Wordpress -> Settings -> Schema App and add your Publisher Type (Organization or Person), Your Name and Your Logo and click Save Changes. Guidelines are included on the page to guide you.
Note: Google's Structured Data Testing Tool shows an error if you pick Person as the Publisher type.
The error for Person as publisher is because of an inconsistency between 1) the schema.org definition of publisher can be Person or Organization and 2) Google AMP use case restricts the Publisher to Organization only.
The conflict is that Person does not have a logo, only image property. Over the long term, I think Google's Testing Tool will change to match the schema.org markup and so we provide the both options. In summary, if you pick Person expect an error for the AMP use case because it expects Logo. This is only really a problem if you're trying to setup AMP which has additional technical requirements beyond the scope of Schema App.