Problem with pdb Oracle 12c
In the root container you can switch the current session to a specific PDB with

ALTER SESSION SET container=orcl;


If you want to actually connect to a specific container (because the user only exists in that container or you have an application which should not know about containers) then you have to connect to the actual net service for the specific PDB. You can use lsnrctl service or check the default tnsnames.ora. There is a good article about this.

This requires some preparation, so check out the Oracle documentation for the concepts as well, but in essence you would have to use a TNS alias or connection description specifying SERVICE_NAME=PDB1 (in your case probably orcl, although that’s a uncommon name for a PDB) instead of a SID or the CDB net service name.