Invalid username/password when trying to pluggable database using DBLINK

I am upgrading database 12.1.0.2 to 19.3. I successfully upgrade one PDB database using DBLINK. When I try to upgrade another database hosted on different server. I created a user in 12.1.0.2 Database

create user c##pdb identified '*' default tablespace users temporary tablespace temp CONTAINER=ALL;

grant create session, create pluggable database, sysoper to c##pdb;

On Target DB - 19c,

create public database lnkdb connect to c##pdb identified '*' using 'TNS'

I am able to successfully access 12c DB using dblink

select sysdate from dual@lnkdb;

SYSDATE

-----------------

02-NOV-20

When i try to create the pluggable database using below command.