Databricks SQL supports read-only query federation to PostgreSQL on serverless and pro SQL warehouses. I would check first you are using the right flavor of SQL warehouse. Could you post the code you are using (without credentials)?
DROP TABLE IF EXISTS postgresql_table;
CREATE TABLE postgresql_table
USING postgresql
OPTIONS (
dbtable '<table-name>',
host '<database-host-url>',
port '5432',
database '<database-name>',
user secret('postgres_creds', 'my_username'),
password secret('postgres_creds', 'my_password')
);