MailChannels and Turnstile validation not working when combined 405 error

import mailChannelsPlugin from "@cloudflare/pages-plugin-mailchannels";

const handleMailChannelsPlugin = async (context) => {
  //Turnstile
  const request = context.request;
  if (request.method === 'POST') {
    console.log("enter hmp");
    const body = await request.formData();
    // Turnstile injects a token in "cf-turnstile-response".
    const token = body.get('cf-turnstile-response');
    const ip = request.headers.get('CF-Connecting-IP');

    // Validate the token by calling the "/siteverify" API.
    let formData = new FormData();
    formData.append('secret', '***');
    formData.append('response', token);
    formData.append('remoteip', ip);

    const result = await fetch('https://challenges.cloudflare.com/turnstile/v0/siteverify', {
      body: formData,
      method: 'POST',
    });
    const outcome = await result.json();
    if (!outcome.success) {
      console.log("turnstile invalid");
      return new Response('The provided Turnstile token was not valid!');
    }
    console.log("turnstile valid");
  }
  console.log("return plugin");

  //MailChannel
  return mailChannelsPlugin({
    personalizations: [
      {
        to: [{ name: "XXX", email: "****" }],
      },
    ],
    from: {
      name: "*****",
      email: "*****",
    },
    subject: "New Contact",
    respondWith: () => {
      console.log('sending response');
      return new Response(
        `Thank you for showing interest in our product.`
      );
    },
  })(context);
};

export const onRequest = [handleMailChannelsPlugin];