Downloading the response from an api call as a csv onClick

I am attempting create a button for downloading a csv file when an item is selected from a dropDown list. Ive done this before but the response returned this time is different than what im use to. I could use some help understanding how to format things to correctly download and display the data in a csv file when the api is hit.

so far I have an onClick function that looks like this:

const onDownloadReport = (type) => {
    const org = type === "All" ? "" : type;
    api.providerPayroll
      .reports({
        date: activePayPeriod,
        org: org,
      })
      .then((res) => {
         window.open("data:text/csv;charset=utf-8," + res);
      });
  };

this works to download the csv file. However it doesnt contain the actual data in the response it shows null in the csv. When i try to console out the res I get null as well. Im not sure what Im missing here for capturing the response.

If I need to add more information on this please let me know.

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