Thank you for pointing out the root of the issue @Lukasz Szozda and @Frank Heikens

In PostgreSQL, unquoted identifiers are automatically folded to lowercase. So, this command:

CREATE ROLE myDatabase_IntegrationServicesAccount LOGIN WITH PASSWORD 'test@12345';

is actually interpreted as :

CREATE ROLE mydatabase_integrationservicesaccount LOGIN WITH PASSWORD 'test@12345';

However, if you explicitly create the role with double quotes, then PostgreSQL preserves the exact case, making the role name case-sensitive.

DROP USER "myDatabase_IntegrationServicesAccount";

This will correctly identify and drop the role with exact casing.