There was an email notification received from the Veeam B&R server stating that one of the VM replication job had failed with the following error:
Error: Failed to open VDDK disk [[Datastore_Name] VM_replica/VM2-000001.vmdk] ( is read-only mode – [false] ) Logon attempt with parameters [VC/ESX: [vCSA_Name];Port: 443;Login: [domain\account_name];VMX Spec: [moref=vm-40195];Snapshot mor: [snapshot-112166];Transports: [nbd];Read Only: [false]] failed because of the following errors: Failed to open disk for write. Failed to download disk. Reconnectable protocol device was closed. Failed to upload disk. Age
The first thing done was to log into the Veeam backup server and open the Veeam Backup & Replication console. 
Under the Home, navigate to the Replicas, search for the VM. Then highlight it and right click and open the properties. It will show all the replica jobs which are snapshots on the replica VM in vSphere.
The two last replica job shows that they were incomplete. This sometimes indicate that there was a problem with the snapshot that was created. Logon to the vSphere web client and check the snapshot manager for the replica VM (the default naming convention is “VMName_replica“). Open the option Snapshots–>Manage Snapshots and you will expand the snapshots until you reach the last two set before “You are here”.
In the image, you will notice that the snapshot names “Veeam Replica Working Snapshot” which indicate that the snapshot was not completed. To eliminate the job continue failing is to delete all the snapshots with the title “Veeam Replica Working snapshot” and rerun the job from veeam so it can recreate the snapshot. If these snapshot are allowed to remain, the Veeam replica job will continue to fail.
I hope this help to resolve some of the veeam replication job failures.
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