CORS error received in Microsoft Edge Add-on

I am performing Discord OAuth through a browser extension and have successfully performed the flow in Chrome and Firefox. However, I get a CORS error partway through the auth process in Microsoft Edge.

I have confirmed through Discord api docs' github that they have no CORS restriction on their server. When placing an authenticated GET request that returns 200 in Chrome, I get a 403 in Edge. I copy & paste the exact same fetch() request into the extension popup console, so there shouldn't be any experimental error. The request as it appears in the Chrome looks like so:

fetch("https://discord.com/api/users/@me", {
  "headers": {
    "accept": "*/*",
    "accept-language": "en-US,en;q=0.9",
    "authorization": "Bearer [redacted]",
    "sec-fetch-dest": "empty",
    "sec-fetch-mode": "cors",
    "sec-fetch-site": "cross-site",
    "sec-gpc": "1"
  },
  "referrerPolicy": "strict-origin-when-cross-origin",
  "body": null,
  "method": "GET",
  "mode": "cors",
  "credentials": "include"
});

I'm able to place this same request in the browser console of any Edge tab that isn't an Edge add-on, and it successfully returns 200 with body data. Only in the Edge add-on does the request fail. Here's an image of the failure message.

Does anyone have experience with CORS errors in Edge add-ons? I doubt the error is related to Discord specifically, but I suppose that could be possible.