I face problem when I try to add new node in the DAG exchange 2013 as the following error:
A server-side database availability group administrative operation failed. Error The operation failed. CreateCluster errors may result from incorrectly configured static addresses. Error: An error occurred while attempting a cluster operation. Error: Node node-name is already joined to a cluster..
Could you check if there already is a Exchange server CN in your Active Directory with the same name as the server you're trying to add? For this you need to connect to the Configuration scheme with ADSI Edit. Then browse to the CN=Servers folder like the screenshot I've added to this post.
You could also run Get-DatabaseAvailabilityGroup and Get-Cluster to check if there is already a Cluster Object and/or DAG active.