Please try this
- make sure /etc/hosts is well populated across all the nodes ( DNS , reverse DNS is workign fine)
- qmgr -c “set server flatuid=true”
- 
edit $PBS_HOME/mom_priv/config (restart pbs_mom services after updating this file) 
 $clienthost HPC
 $clienthost node0
- 
create a file called clientfile on the PBS Server/Scheduler host in the below location 
 /var/spool/pbs/sched_priv/clientfile
cat  /var/spool/pbs/sched_priv/clientfile
$clienthost node0
- Start the PBS Scheduler as below manually or by updating the startup scripts
 /opt/pbs/sbin/pbs_sched -c /var/spool/pbs/sched_priv/clientfile
 [ if the pbs_sched has already started, then kill the pbs_sched daemon, and start it manually as above ]