Delivery Customization Extension not workig

[joppx25]

Hi there,
I created a delivery customization extension to sort a liverates from a custom app but the current problem is it didn't work when I add this one to the shopify plus store. I'm new to shopify and have limited idea on graphql stuff. There's a section in the tutorial that I didn't do because I don't want client to install another app(which is the graphiql app). I added this mutation.graphql file to my extension directory and redeploy the extension but still it didn't work. Any idea what's the problem here? Thanks