Nothing seems to work in the sandbox

[dj_gerbil]

I've been trying to create a listing via the RESTful API and it's been everything but RESTful!

So I've been following a guide from https://stackoverflow.com/questions/63853430/how-to-create-listing-in-ebay-sandbox which says:

Create Payment, Fulfillment, and Return policies for your sandbox account. For this, you may call their respective APIs or you can use their API Explorer which has sample policy requests ready to be executed or, easiest of all, you can manage your business policies from the sandbox website

So I've managed to create the Fulfillment and Return Policies, but Payment just won't work. In the sandbox it keeps saying "PayPal is Required" but there's no options to add it or anything and the API Explorer just gives a non-helpful error about the Payment Method and I've tried ALL of the ones in the list.

{
  "errors": [
    {
      "errorId": 20403,
      "domain": "API_ACCOUNT",
      "category": "REQUEST",
      "message": "Invalid .",
      "longMessage": "Invalid payment detail",
      "inputRefIds": [
        null
      ],
      "parameters": [
        {
          "name": "PAYMENT_METHODS_NOT_FOUND",
          "value": "Payment Methods not found for the given request Criteria"
        }
      ]
    }
  ]
}

The guide goes on to say about creating a location and again the API hasn't dissapointed with it's non-helpful error of:

"errorId": 25802,
      "domain": "API_INVENTORY",
      "category": "REQUEST",
      "message": "errorDetails(20400/Invalid request.)"

The only time I got anything different was when I changed the Country to an incorrect one.

So now I'm stuck because I can't create an offer without the policies or a location.

Please Help.