Oracle 12c PDB Cloning with RMAN - Aux DB connection issues
$ oerr rman 6814
6814, 1, "cannot connect to pluggable database %s"
// *Cause:  An error was received when connecting to database because
//          the database is a pluggable database.
// *Action: Connect to the root database and retry the command.


That is not how you clone a PDB.

Duplicating PDBs

When you duplicate one or more PDBs, RMAN also duplicates the root (CDB$ROOT) and the seed database (PDB$SEED). The resulting duplicate database is a fully functional CDB that contains the root, the seed database, and the duplicated PDBs.

And this is how you do it: 

Cloning a Remote PDB or Non-CDB

Example:

CREATE PLUGGABLE DATABASE pdb02 FROM pdb01@pdb01_link;