When trying to connect to a database via SCAN listener in a RAC environment with sqlplus, an ORA-12514 error is thrown. Tnsping can resolve the connect string. Whereas connecting to the same database over node listener with sqlplus succeeds.
One possible reason could be, that the parameter remote_listener of the database to be connected is not set to SCAN listener of RAC cluster.
So try to set remote_listener to SCAN_LISTENER_HOST:SCAN_LISTENER_PORT like (e.g. host is scan_host, port is 1521):
alter system set remote_listener = 'scan_host:1521' scope=both;