As announced back on March 12, 2015 Microsoft has discontinued the functionality of its Yammer App for SharePoint 2013 and Office 365 (SharePoint Online) on September 15th. This means the App will stop working completely and will no longer be supported. Customers on SharePoint 2013 or SharePoint Online must migrate to Yammer Embed. Here’s a step-by-step guide to move to Yammer Embed.
The Yammer Web Part for SharePoint 2010 will be discontinued on March 15th, 2016. The Web Part will stop working on this date and will no longer be supported.
Please note that only SharePoint Server 2013, SharePoint Server 2016 and Office 365 will support Yammer Embed.