Hi

I am not sure but looks like you need to do

What are the contents of
$ORACLE_HOME/opmn/logs/ons.log file

Check the file permissions on the node where it is working

ls -ltr $ORACLE_HOME/opmn/lib/lib*.so

You might have to do on the other node this

$ORACLE_HOME/opmn/bin/opmnctl stopall
chmod o+rx $ORACLE_HOME/opmn/lib/lib*.so
$ORACLE_HOME/opmn/bin/opmnctl start

Please be careful as i am just speculating about this here as i am not completely sure

regards
Hrishy