For anyone else with the same issue, it seems to be that Google Apps Scripts returns a redirect to the Shopify call for some reason. I implemented the same functionality using Cloudflare Workers, which does require some set up on Google Cloud but any...

Hi Sibari. Were you able to solve this issue? I'm also experiencing something very similar.

I have a development store: carrierservicetesting.myshopify.com I have enabled a carrierService, and I have double checked that it's active. I created it using the GraphQL API, and if I request carrier services, I receive it, so I know it's there. Th...