You need to check what “ROLES” your Postgres installation has available, and possibly create a suitable one. PostgreSQL docs say:
In order to bootstrap the database system, a freshly initialized system always contains one predefined role. This role is always a “superuser”, and by default (unless altered when running
initdb) it will have the same name as the operating system user that initialized the database cluster. Customarily, this role will be namedpostgres.
This means it is neither guaranteed for every PostgreSQL installation to have the postgres “role” nor it is guaranteed for it to have “postgres” as password, even if it exists.
