http POST request works in VSCode testing, but doesn't work with node-fetch in lambda function

I have a lambda function that moderates input before calling the openai API. It works perfectly in sam local, as well as directly in VSCode (not through my lambda url). When I use my lambda function, I get this error:

{
  "error": {
    "code": null,
    "param": null,
    "message": "'input' is a required property",
    "type": "invalid_request_error"
  }
}

Here is the function that works locally (using SAM CLI invoke)

const moderationResponse = await fetch('https://api.openai.com/v1/moderations', {
            method: 'POST',
            headers: {
                'Content-Type': 'application/json',
                'Authorization': `[PRIVATE]`
            },
            /* body is stringified before this step
               and looks like { input: inputText }
            */
            body: moderationBody
        })

I'm not really getting any worthwhile logs to try to fix anything.