Sandbox account balance not increasing in testing

[Sacredwisp]

I'm currently testing the smart payment buttons for my website.  I'm creating the order on the client side, then sending the order ID to my server and capturing it there.  It seems to work mostly fine, as the funds are taken from the seller's account and the transaction is recorded in the merchant account, but the balance in the merchant account is not updating.  It also says that all the transactions are completed in the summary.  However, in the activity log, it almost seems like the funds are inserted then removed?  After each payment, the balance updates, then it seems as though it resets back to $1000, which was the default amount set to the account.  Does anyone have any insight as to what could be causing this?

[Sacredwisp]

I found that in the transaction capture, I'm getting an error that looks like: 

{
  "name": "AUTHENTICATION_FAILURE",
  "message": "Authentication failed due to invalid authentication credentials or a missing Authorization header.",
  "links": [
    {
      "href": "https://developer.paypal.com/docs/api/overview/#error",
      "rel": "information_link"
    }
  ]
}

and it is effectively doing a refund.  However, I'm not really sure what I'm supposed to be doing with this.  In the docs for the server side checkout SDK (https://developer.paypal.com/docs/checkout/reference/server-integration/setup-sdk/#pass-the-partner-...), it doesn't mention anything about authentication.  I found some other docs with information about a Bearer token, but I don't know how it fits in with this specific SDK.  Also, it looks like the only way to get the token is through a cURL command, but I'm using NodeJS.  If someone has insight on what I need to do next, that would be great.