Payment error

[HVENetworks]

So I make this request to the orders api

{
  "intent": "CAPTURE",
  "purchase_units": [
    {
      "amount": {
        "currency_code": "USD",
        "value": "1.00"
      },
      "payee": {
        "email_address": "*receiver email*"
      }
    }
  ]
}

and I get a response like this

{
    "id": "96R50914BA6824544",
    "links": [
        {
            "href": "https://api.sandbox.paypal.com/v2/checkout/orders/96R50914BA6824544",
            "rel": "self",
            "method": "GET"
        },
        {
            "href": "https://www.sandbox.paypal.com/checkoutnow?token=96R50914BA6824544",
            "rel": "approve",
            "method": "GET"
        },
        {
            "href": "https://api.sandbox.paypal.com/v2/checkout/orders/96R50914BA6824544",
            "rel": "update",
            "method": "PATCH"
        },
        {
            "href": "https://api.sandbox.paypal.com/v2/checkout/orders/96R50914BA6824544/capture",
            "rel": "capture",
            "method": "POST"
        }
    ],
    "status": "CREATED"
}

when I go to the payment site, I log in with my second sandbox account, and it says "We're sending you back to *receiver email* to complete this purchase."

then it goes to the payment form again. Then it repeats that message once more, but this time it redirects me to a page saying "We’re sorry Things don’t appear to be working at the moment."

what am I doing wrong?