Have you verified that the Shopify shop has fulfillment services properly defined? And have you verified your API credentials have been granted this access scope? https://shopify.dev/docs/admin-api/access-scopes
I honestly have no idea what project, library, wrapper, etc. that this api_client is. If it's something like this --> https://shopify.github.io/shopify-app-cli/ then have you reviewed any "getting started" documentation? Regardless what this tool is, you have to install something in the Shopify shop to get things going. And part of that install process involves getting API credentials as well as using OAuth as a Shopify shop user to authorize access scopes --> https://shopify.dev/tutorials/authenticate-with-oauth.
Okay, taking this a step or two back still. I assume you have a Shopify shop, and that you had to install an app into it in order to be able to use your API credentials, right? The step of that installation process that allowed the app to reside in the Shopify shop involved a logged-in Shopify user account authorizing the app access to the shop. Where is displays that the app will have access to customer, products, order, etc. That step is where the access scopes are defined. That step needed to include the access scope that your api_client is kicking back as being missing.