Unable to auth into AppSync GraphQL api from Lambda using IAM and AppSyncClient

Question

I'm using an amplify stack and need to perform some actions to my graphql api which has dynamodb behind it. The request in my lambda function returns an Unauthorized error: "Not Authorized to access getSourceSync on type SourceSync", where getSourceSync is the gql query and SourceSync is the model name.

My schema.grapqhl for this particular model is set up as following. Note auth rule allow private provider iam:

type SourceSync @model (subscriptions: { level: off }) @auth(rules: [
    {allow: private, provider: iam}
    {allow: groups, groups: ["Admins"], provider: userPools},
    {allow: groups, groups: ["Users"], operations: [create], provider: userPools},
    {allow: groups, groupsField: "readGroups", operations: [create, read], provider: userPools},
    {allow: groups, groupsField: "editGroups", provider: userPools}]) {
    id: ID! @primaryKey
    name: String
    settings_id: ID @index(name: "bySettingsId", queryField: "sourceSyncBySettingsId")
    settings: Settings @hasOne(fields: ["settings_id"])
    childLookup: String
    createdAt: AWSDateTime!
    updatedAt: AWSDateTime!
    _createdBy: String
    _lastChangedBy: String
    _localChanges: AWSJSON
    readGroups: [String]
    editGroups: [String]
}

My lambda function's role has the following inline policy attached to it. (Actual ID values have been omitted for security purposes on this post):

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Action": [
                "appsync:GraphQL"
            ],
            "Resource": [
                "arn:aws:appsync:us-east-1:111myaccountID:apis/11mygraphqlapiID/*"
            ],
            "Effect": "Allow"
        },
        {
            "Action": [
                "appsync:GetType"
            ],
            "Resource": [
                "*"
            ],
            "Effect": "Allow"
        }
    ]
}

And finally my lambda function is set up as follows with a simple query test:

/* stuff */

"use strict";
const axios = require("axios");
const awsAppSync = require("aws-appsync").default;
const gql = require("graphql-tag");
require("cross-fetch/polyfill");
const { PassThrough } = require("stream");
const aws = require("aws-sdk");

aws.config.update({
    region: process.env.AWS_REGION,

});

const appSync = new aws.AppSync();

const graphqlClient = new awsAppSync({
    url: process.env.API_GRAPHQLAPIENDPOINTOUTPUT,
    region: process.env.AWS_REGION,
    auth: {
        type: "AWS_IAM",
        credentials: aws.config.credentials,
    },
    disableOffline: true
});

exports.handler = async (event, context) => {
    
    console.log('context :: '+JSON.stringify(context));
    
    console.log('aws config :: '+JSON.stringify(aws.config));
    
          const sourceSyncTypes = await appSync
          .getType({
            apiId: process.env.API_GRAPHQLAPIIDOUTPUT,
            format: "JSON",
            typeName: "SourceSync",
          })
          .promise();
          console.log('ss = '+JSON.stringify(sourceSyncTypes));
    
    try {
    const qs = gql`query GetSourceSync {
  getSourceSync(id: "ov3") {
    id
    name
  }
}`;
    const res = await graphqlClient.query({query: qs, fetchPolicy: 'no-cache'});
    console.log(JSON.stringify(res));
    
    }
    catch(e) {
        console.log('ERR :: '+e);
        console.log(JSON.stringify(e));
    }
    
};