Backup job failed

Well, that message does nothing to help with your issue.  What version of Veeam are you using?  What virtualization are you using?  Did you check the logs for further errors or direction - C:\ProgramData\Veeam\xxxx?

Posting one line for the title and details does not help anyone give you direction.  Please ensure to read the community rules.

13.0.2.29 veeam version.,nutanix,

Backup job status is showing failed

Reason:Cannot find any available cluster nodes                               This is the error I am seeing and data processed is 0 and read is 0   

Have you thought about upgrading to the latest 13.1.2 release to test?  Is the Nutanix plugin the latest one for that version of Veeam?  I would suggest opening a support ticket with this post, as the community is NOT technical support.  We can offer suggestions, but for a proper answer or troubleshooting support, the direction to take is opening a ticket.