Full Redirect URI Doesn't Provide Valid Access Token

I currently am trying to integrate Zoho Vault APIs into my .net application. I set up a web server application in the Zoho API and received a clientID and clientSecret. I set 2 redirect uri's in my application, #1 is the base path of the application. #2 is the full url. #2 includes a path to a callback function in my .net application that is supposed to process the authorization code after authorization to acquire an access code. When I use redirect uri #1 (just the base path of my application which takes me to the homepage) I am able to receive a valid authorization code, valid access code, and get the response I want. However, whenever I use redirect uri #2 (the full path which includes the callback function) I always receive and "invalid code" error. I have copied my client id and client secret exaclty and am using them as necessary. I have copied both redirect uri's exaclty into my API Developer Console application. So I know for a fact that there are no typos. I am using the ZohoVault.secrets.READ scope and I am following the steps in this link https://www.zoho.com/vault/api/. Also, I would very much appreciate some help in decrypting what is encrypted within the responses. I have seen on some forums that you can provide some files that will help. I would greatly appreciate any help! Thank you!

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