role "my_account" does not exist

Hello!

Following this web page
<https://ubiq.co/database-blog/create-user-postgresql/>, I have tried to
create a new role/user, but to no avail.

After typing the following command : /*createuser --interactive
--pwprompt*/ I get the following questions:

Enter name of role to add: company_name
Enter password for new role: xxxxxxx
Enter it again: xxxxxxx
Shall the new role be a superuser? (y/n) y

Than this error is displayed :
*/createuser: error: connection to server on socket
"/var/run/postgresql/.s.PGSQL.5432" /**/
/**/failed: FATAL:  role "my_debian_login_account_name" does not exist/*

How/ever, this issue is not really relevant/, per se, since I am able to
create roles once I log in PostgreSQL-15. Nonetheless, if the service
exist, why not usu it. If the services exist and is not working, could
it be that there is a problem that will come apparent later on, when
unlike now, it would be during a critical moment. Thus the question,
what can I do to resolve this issue?
Is there something I am missing?

Thanks