18cXE on CentOS 7: can’t connect to XEPDB1

hi all,
installed 18c XE on CentOS 7, all things done and I can connect using:
sqlplus sys/ora1234 as sysdba
but even after created an entry in “tnsnames.ora” for XEPDB1 and issued below 2 ALTER PLUGGABLE commands as per documentation i can’t using: sqlplus sys/ora1234@XEPDB1 as sysdba

SQL> ALTER PLUGGABLE DATABASE ALL OPEN;
SQL> ALTER PLUGGABLE DATABASE ALL SAVE STATE;

only can connect using :

ALTER SESSION SET CONTAINER=xepdb1;

i have to install and use Oracle Apex with ORDS on this machine, so please help.
regards