"ORA-01033: Oracle initialization or shutdown in progress" error after PC restart
The tutorial you linked uses the multitenant architecture with pluggable databases. I quickly read through the tutorial, and it does not cover this topic, but pluggable databases do not open automatically with the root container, unless specified otherwise. My guess is that you tried to connect the pdborcl pluggable database. Run the below:

select name, open_mode from v$pdbs;


If you see pdborcl, with open_mode = MOUNTED, issue the below:

alter pluggable database pdborcl open;


Now try connecting again. If your database version is 12.1.0.2, you can use the below after opening the pluggable database to make it start automatically the next time the whole database is restarted:

alter pluggable database pdborcl save state;


If your database version is 12.1.0.1, the above feature is not available, and you need to open the pluggable database each time manually, or create an after startup trigger in the database, for example:

CREATE OR REPLACE TRIGGER open_pdbs 
  AFTER STARTUP ON DATABASE 
BEGIN 
   EXECUTE IMMEDIATE 'ALTER PLUGGABLE DATABASE ALL OPEN'; 
END open_pdbs;
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