Just trying to bump this thread up, in case somebody can help
Post the listener.ora file and output of below commands :
srvctl config scan_listner
srvctl status listener
Enable client side trace in sqlnet.ora and past the out put of trace file..
You can also try setting local_listener parameter in spfile
Set LOCAL_LISTENER to the fully qualified domain name (e.g. node-VIP.example.com):
The SQLNET.ORA will now look like the following
TRACE_LEVEL_CLIENT = SUPPORT
TRACE_UNIQUE_CLIENT = on
TRACE_LEVEL_SERVER = SUPPORT
TRACE_DIRECTORY_CLIENT = C:\TEMP
TRACE_FILE_CLIENT = CLIENT
TRACE_DIRECTORY_SERVER = C:\TEMP
TRACE_FILE_SERVER = SERVER
TRACE_TIMESTAMP_ CLIENT = ON
Many thanks for your help and suggestions.
The issue was with firewall setting of "deep packet inspection" being switched on. Once turned off, the issue was resolved.