Mutation through API fails, but works from web portal

Hey! I'm trying to get some help figuring out why a mutation works in the AWS AppSync web portal, but fails when I try to use the API within one of my lambda tests.

Schema:

type OrganizationLink @model @searchable @auth(rules: [
    {allow: groups, groups: ["Admin"]},
    {allow: groups, groupsField: "readGroups", queries: [get, list], mutations: null},
    {allow: groups, groupsField: "writeGroups" mutations: [update, delete], queries: null}
]) {
    id: ID!
    type: OrganizationType
    school: School @connection(name: "SchoolOrganization")
    district: District @connection(name: "DistrictOrganization")
    organization: Organization @connection(name: "OrganizationConnection")
    readGroups: [String]
    writeGroups: [String]
}

Auto-Generated Schema from backend/.../schema.graphql:

...
createOrganizationLink(input: CreateOrganizationLinkInput!): OrganizationLink

...
onCreateOrganizationLink: OrganizationLink @aws_subscribe(mutations: ["createOrganizationLink"])

...
input CreateOrganizationLinkInput {
  id: ID
  type: OrganizationType
  readGroups: [String]
  writeGroups: [String]
  organizationLinkSchoolId: ID
  organizationLinkDistrictId: ID
  organizationLinkOrganizationId: ID
}

Mutation:

mutation createLink($organizationID: ID, $schoolID: ID){
	  createOrganizationLink(input:{
	  	type: School
		organizationLinkOrganizationId: $organizationID
		organizationLinkSchoolId: $schoolID
	  })  {    id  }
}

API Call method:

const resp = await fetch(graphqlApi, {
		body,
		credentials: 'include',
		headers: {
			accept: '*/*',
			authorization: AccessToken,
			'content-type': 'application/json',
		},
		method: 'POST',
		mode: 'cors',
	});

API Request Body:

{
    "operationName": "createOrganizationLink",
    "query": "\n\t\tmutation createLink($organizationID: ID, $schoolID: ID){\n\t\t  createOrganizationLink(input:{\n\t\t  \ttype: School\n\t\t\torganizationLinkOrganizationId: $organizationID\n\t\t\torganizationLinkSchoolId: $schoolID\n\t\t  })  {    id  }\n\t}",
    "variables": {
        "organizationId": "5432eca5-1018-4bf1-ba60-679557ca1e3c",
        "schoolId": "ed1fbead-1906-4cc8-b5b3-64b3e9995501"
    }
}

Response Error:

url: 'https://XXXXXXXXXX.appsync-api.us-west-2.amazonaws.com/graphql',
     status: 400,
     statusText: 'Bad Request',

errorType: 'BadRequestException',
message: 'No operation matches the provided operation name createOrganizationLink.' } ] }

I don't understand how the operation isn't being found, when I am using the exact same operation in the web portal. The operation to create an organization link is clearly in the schema as well. I use this same function to do other mutations prior to this one and they work flawlessly. Any hints would be greatly appreciated...please let me know if any additional information is needed.

Edited by: markta on Apr 19, 2019 2:03 PM