Apollo client:codegen does not create types for inputs

Question

I am new to GraphQL and is currently using Apollo Client on our TypeScript React project. I am currently trying to generate types using client:codegen command and it is not including the Inputs on Mutations. This is currently the script I have in my package.json

"codegen:auth-api": "apollo client:codegen --target typescript --includes=\"./src/graphql/auth-api/**/*.ts\" --outputFlat --endpoint=\"https://frontend-engineer-onboarding-api-thxaa.ondigitalocean.app/graphql\" \"src/types\"",

That outputs this

import { SignUpInput } from "./globalTypes";

// ====================================================
// GraphQL mutation operation: SignUp
// ====================================================

export interface SignUp_signUp {
  __typename: "Authentication";
  token: string;
}

export interface SignUp {
  /**
   * ### Description
   * Sign up a user and get an access token if successful.
   * 
   * ### Error Codes
   * `BAD_USER_INPUT` - Email address already used.
   */
  signUp: SignUp_signUp;
}

export interface SignUpVariables {
  input: SignUpInput;
}

The problem above is that globalTypes.ts is empty when it should have something like below

interface SignUpInput {
...
}

This is a sample of my mutation code

export const SIGN_UP = gql`
  mutation SignUp($input: SignUpInput!) {
    signUp(input: $input) {
      token
    }
  }
`;

Is there something I am missing? I've also tried passing --passthroughCustomScalars but that just removes custom scalars. I apologize if I could not find any answer here on SO and Thanks in advance for your help.