NDMP backups are failing with error code 99. In detail status it is mentioned that failure is due to configuration failure(2) : RPC Error.
vfiler is UP and working fine. It is online and have much space. It is a NAS vfiler.
It looks like primary communication itself failing, try following
1> Confirm tpautoconf -verify filer_ip_address and tpautoconf -verify filer_name works
2> Add hosts file shortname and fqdn entries on both Server and Filer side if required.
3> Confirm forward and reverse lookup (shortname & fqdn ) works from both Server and Filer side.
4> Run bpclncmd -clear_host_cache on Master -Media Server
5> Retry backup.