The Compatibility Checker found one or more Office Add-in-related compatibility issues.
Note: New name for apps for Office - Office Add-ins. We are currently updating our products, documentation, samples, and other resources to reflect the platform name change from "apps for Office and SharePoint" to "Office and SharePoint Add-ins". We made this change to better distinguish the extension platform from Office apps (applications). While these changes are taking place, the dialogs and messages you see in your application might be different than what you see in this article.
Important: Before you continue saving the workbook to an earlier file format, you should address issues that cause a significant loss of functionality so that you can prevent permanent loss of data or incorrect functionality.