In order to allow the communication between x-Integrator and the store, webservices in PrestaShop need to be enabled.
You can enable webservices in the PrestaShop's back-office panel panel.
Go to "Advnaced Parameters -> Webservice" and select the option "Enable PrestaShop's werbserwice": YES.
Then, click "Add new webservice key":
Then set the permissions:
And submit the form.
In the end, send the generated key to us so that we can setup the synchronization or log in to the Xintegrator's panel and paste the key on the shop's settings page: