lambda@edge accessing lambda function via api gateway getting {"message":"Forbidden"}

I am able to access the Lambda function directly or via the custom domain with a 200 status. However, configuring a Lambda@edge function to redirect to the custom origin results in a {"message":"Forbidden"} response

The API is open so its not an authorizer issue

Here is the redirect code

'use strict';
exports.handler = (event, context, callback) => {
     const request = event.Records[0].cf.request;
     if (request.headers['x-ssr-token'] && request.headers['x-ssr-host'] && request.headers['x-query-string']) {
       request.querystring = request.headers['x-query-string'][0].value;
       request.origin = {
           custom: {
               domainName: 'myapi.mydomain.com',
               port: 443,
               protocol: 'https',
               readTimeout: 20,
               keepaliveTimeout: 5,
               customHeaders: {},
               sslProtocols: ['TLSv1', 'TLSv1.1', 'TLSv1.2'],
               path: '/https%3A%2F%2F' + request.headers['x-ssr-host'][0].value
               }
       };
    }
    callback(null, request);
};