First, the Office Store no longer accepts add-ins that use the 1.0 version of the manifest. This change went into effect on November 18th, 2015. Most tools and examples no longer use the 1.0 manifest format so for the most part, all new submissions should pass validation when you submit the add-in to the store.
If you update an existing add-in posted in the Office Store, it must use the 1.1 manifest format and the 1 or 1.1 reference to office.js or else it will fail validation. This means the update will be rejected, but the existing add-in will remain in the store.
Starting in February 2016, existing Office Store add-ins that use the 1.0 manifest format will not be ranked as well on the Office Store home page and search rankings as the same add-in that uses the 1.1 manifest format.
If you are using Visual Studio 2013 to develop Office add-ins, then please ensure that you have the latest Microsoft Office Developer Tools updates installed. You can download the latest updates in Visual Studio 2013 by going to Tools -> Extensions and Updates -> Updates. If you are using Visual Studio 2015 to develop Office add-ins, the default Visual Studio 2015 installation comes with the Microsoft Office Developer Tools. If you customized your install, you can separately download the Microsoft Office Developer Tools.
Another change that has happened is that the Office Store will no longer accept add-ins that reference the office.js 1.0 resource. All new add-in submissions should use the https://appsforoffice.microsoft.com/lib/1/hosted/office.js resource. Most samples and tools have been updated to use the new resource so for most of you starting off, your add-in should be fine. You may have seen examples that reference the /1.1/ resource, https://appsforoffice.microsoft.com/lib/1.1/hosted/office.js. That’s fine for now but from now on, you should use the /1/ resource.
Are you using MicrosoftAjax.js (http://ajax.microsoft.com/ajax/4.0/1/MicrosoftAjax.js) in your add-in? As of the posting date of this blog post, office.js automatically loads MicrosoftAjax.js. MicrosoftAjax.js adds latency to app load times that may affect the add-in user experience. We’ve decided to remove MicrosoftAjax.js from the office.js loader since many add-ins don’t make use of it. The /1/ and /1.1/ office.js libraries will no longer load MicrosoftAjax.js starting in January 2016. In the meantime, you should update your add-in to manually add references to MicrosoftAjax.js if you are using it. If you’re unsure of whether your add-in is using it, we created a temporary resource at https://appsforoffice.microsoft.com/lib/1-nomsajax/hosted/office.js that doesn’t load MicrosoftAjax.js. We expect that this resource will be available starting December 10th, 2016. Use this resource to test your add-in to see whether it is using MicrosoftAjax.js.
Michael Mainer, Senior Content Publisher, Microsoft