All serverless functions return error 1101 on CF worker

Any serverless function I use returns error 1101 despite Cloudflare’s ‘Preview’ window displaying the output of my functions correctly. To test, I used Cloudflare’s “HTTP Handler” template, which I pasted below and simply returns “Hello World.” This also outputs error 1101.

export default {
  async fetch(request, env) {
    return new Response("Hello world")

The URL of this CF worker is
And, as you can see in the attached image, the page returns with status code 200 (atleast on the CF worker editor)

Any ideas? Thanks!