ORA-28040 no matching authentication protocol

There is connection problem to Oracle Database 12c with clients below 12c version, When I am trying to connect oracle database 12.2 with PL/SQL Developer appears next error

ORA-28040 no matching authentication protocol

Solution is to create a sqlnet.ora on server where database reside in the $ORACLE_HOME/network/admin location with the following parameter:

SQLNET.ALLOWED_LOGON_VERSION_SERVER=9
SQLNET.ALLOWED_LOGON_VERSION_CLIENT=9

or if sqlnet.ora file exist under $ORACLE_HOME/network/admin
append SQLNET.ALLOWED_LOGON_VERSION_SERVER=9 and SQLNET.ALLOWED_LOGON_VERSION_CLIENT=9 and save it.
it means client with version 9 or later can connect to database, you can use numbers according oracle clients versions which correspondingly means minimum version of client can connect to database
If you have installed Grid infrastructure with different user than oracle, then you need also to do above procedures for GRID_HOME's sqlnet.ora file.

Finally stop and start listener to be useful sqlnet.ora parameters.