Ah thank you! Got it to work. The trick was form data.

Notes: the ids parameter is form data. You can copy the js code snippet from here https://rapidapi.com/listennotes/api/listennotes?endpoint=5c2be887e4b0b136b4745649 and test if it works on your side.

I just ran with the same episode ids. It worked. Could you test without using javascript? as I said in my previous reply: use CURL to test. This can give you some insight whether it’s the problem on the API side or it’s the problem on the programming language side.

Here’s the JS request I made:

  const episodesRequest = new Request(
    `https://listennotes.p.rapidapi.com/api/v1/episodes`, {
      headers: new Headers({
        "X-Mashape-Key": "XYZ",
        "Content-Type": "application/x-www-form-urlencoded",
        "Accept" : "application/json"
      }),
      method: 'POST',
      params: JSON.stringify({ids: 'c577d55b2b2b483c969fae3ceb58e362,0f34a9099579490993eec9e8c8cebb82,b37f33c1ba184f97a479ea794161c221'})
    }
  );

What ids did you try? Can you paste those ids here?

It would be helpful to troubleshoot by just using curl on your side.