Stored Procedure cannot run successfully in SQL Server via SQLAlchemy - sql-server

Question

What I am using
Ubuntu 16.04
Python 3.6
FreeTDS, TDS Version 7.3
SQLAlchemy 1.2.5
Windows server 2012
SQL Server 2008 Enterprise
My purpose
I write code in Python on Ubuntu machine to insert and execute stored procedure on MS SQL Server 2008. I create an order for customer. An order may have many main ingredients, toppings. When finish order, I run a stored procedure to process data to user_order and employee_order.
The stored procedure
In stored procedure, when select data from source tables and process data, if any error is happened, transaction is rolled back.
My code snippet
def process():
engine = get_engine() # my method get engine by connection string
session_maker = sessionmaker(bind=engine.execution_options(isolation_level='SERIALIZABLE'))
session = session_maker()
ref = 'REF0000001'
try:
# Create order
order = Order(id=1, ref=ref)
# Add main ingredients
main1 = Main(order=1, name='coffee')
main2 = Main(order=1, name='milk')
# Topup
topup1 = TopUp(order=1, name='cookies')
topup2 = TopUp(order=1, name='chocolate')
session.add(order)
session.flush()
session.add_all([main1, main2])
session.flush()
session.add_all([topup1, topup2])
session.flush()
session.commit()
except:
session.rollback()
reraise
finally:
session.close()
del session
time.sleep(1)
session = session_maker()
session.execute('EXEC finish_order %a' % ref)
session.commit()
session.close()
del session
And result is
There is no error, but there is no data in user_order and employee_order even though stored procedure finish_order is run.
But, if I run the stored procedure again as a simple query in terminal or SQL Studio Management, the data is imported to destination tables.
Doubts
Is there any chance that data has not been finished inserting into origin tables yet when stored procedure is called?
Please help me with this case.
Thank you!