question

401 is generally tied to expired/invalid token. I would suggest checking your OAuth/acessToken.

C# HttpClient Ex:

var client = new HttpClient();
var request = new HttpRequestMessage(HttpMethod.Get, "https://sandbox.dev.clover.com/v3/merchants/{mId}/orders");
request.Headers.Add("Authorization", "Bearer {accessToken");
var response = await client.SendAsync(request);
response.EnsureSuccessStatusCode();
Console.WriteLine(await response.Content.ReadAsStringAsync());

C# RestSharp Ex:

var options = new RestClientOptions("https://sandbox.dev.clover.com")
{
  MaxTimeout = -1,
};
var client = new RestClient(options);
var request = new RestRequest("/v3/merchants/{mId}/orders", Method.Get);
request.AddHeader("Authorization", "Bearer {accessToken");
RestResponse response = await client.ExecuteAsync(request);
Console.WriteLine(response.Content);