Issues with downloading attachments from cards. 401 error through REST API using RestSharp

So I am trying to create an application that will enable me to input a string and search every card on a specific board for that string in the card names. Once it does that I am creating a new directory on the local server and I want to download all attachments into the new directory. I have everything working as desired with the exception of downloading the attached files. I am getting a 401 error about unauthorized access request.

The fact that I am using RestSharp and scripting in C# which there isn’t really any documentation for the Trello API, but I have attempted to make a request using the methods that I saw listed in this announcement:

Now, one thing that is different for me from the above announcement is that I am not getting a signature at the end of the URL when I make the call to get the attachment information. So I may be doing things a little wrong. I am just in need of some help, because I have no idea what I could be doing incorrectly.

I also don’t know if any of you have experience or have interacted with RestSharp, but it is essentially a wrapper for the HttpClient class in C#. Any help would be greatly appreciated.