You may receive this error in client system when trying connects remote server

# showmount -e
clnt_create: RPC: Program not registered

Be ensure all the nfs server configurations are functional in the system,

If there is no error check in the client system.
# /etc/init.d/nfs restart

Shutting down NFS daemon:                                 [  OK  ]
Shutting down NFS mountd:                                  [  OK  ]
Shutting down NFS quotas:                                   [  OK  ]
Shutting down NFS services:                                 [  OK  ]
Shutting down RPC idmapd:                                  [  OK  ]
Starting NFS services:                                           [  OK  ]
Starting NFS quotas:                                             [  OK  ]
Starting NFS mountd:                                            [  OK  ]
Starting NFS daemon:                                           [  OK  ]
Starting RPC idmapd:                                            [  OK  ]

# chkconfig nfs on

#  chkconfig | grep nfs

nfs              0:off   1:off   2:on    3:on    4:on    5:on    6:off
nfslock         0:off   1:off   2:off   3:on    4:on    5:on    6:off

#  chkconfig | grep rpcbind

rpcbind         0:off   1:off   2:on    3:on    4:on    5:on    6:off

Now you can check it,
# showmount -e

Export list for  /share

Now, mount the files and check it,
# mount  -t nfs /clientshare

#cd /clientshare