This module must be installed on your magento1 website tofix 2 problems : 

1. API stock update issue if you use numerical skus

2. Add webservice to send email for shipments

You can download the module from here : 

https://extensions.boostmyshop.fr/ressources/connect/magento1/bms-magento1-erpcloud-1.0.2.zip

Simply upload the zip content to FTP and refresh magento caches