Dropbox .net SDK, automatic refresh of access token not working

public async Task<string> GetAccessToken(string LicenseServerAddress = null)
        {
            try
            {
                // Short lived ID that allows us to identify ourselves to the casoftkeywebsite
                string SessionID = Guid.NewGuid().ToString("N");

                var redirect = DropboxOAuth2Helper.GetAuthorizeUri(OAuthResponseType.Code, AppKey, RedirectUri, SessionID, false, false, null, false, TokenAccessType.Offline, ScopeList, IncludeGrantedScopes.None, null);

                // Take the user through authentiation
                Process.Start(redirect.ToString());

                string ServerAddress = null;

                // Get the code from casoftkey, we store them there after authentication
                if (!string.IsNullOrEmpty(LicenseServerAddress))
                {
                    ServerAddress = LicenseServerAddress;
                }
                else
                {
                    ServerAddress = m_engine.BorregoEngine.GetCCConfigFileValue("LicenseServerAddress");
                }
                
                Root6LicensingRestClient Client = new Root6LicensingRestClient(ServerAddress);

                var TokenResult = await Client.GetToken("ContentAgent", "!~P8+AF<,v$/z~Mp");

                if (!string.IsNullOrEmpty(TokenResult.error))
                {
                    if (!string.IsNullOrEmpty(TokenResult.error_description))
                    {
                        return TokenResult.error + " : " + TokenResult.error_description;
                    }

                    return TokenResult.error;
                }

                Client.SetAuthenticationToken(TokenResult.access_token);
                ServerResult<DropboxOAuth2Info> result = null;

                int Timeout = 60; // 60 seconds to get the code response
                int TimeoutCounter = 0;

                do
                {
                    TimeoutCounter++;
                    result = await Client.GetDropboxCode(SessionID);
                    System.Threading.Thread.Sleep(1000);
                }
                while ((result == null || result.Data == null) && TimeoutCounter < Timeout && result.OperationResult != enDatabaseOperationResult.Error);

                if (result !=null)
                {
                    if (result.OperationResult == enDatabaseOperationResult.Error)
                    {
                        return "Error retrieving Dropbox code: " + result.error;
                    }
                }
                else if (TimeoutCounter >= Timeout && (result == null || result.Data == null))
                {
                    return "Timed out waiting for the user to authenticate with Dropbox";
                }

                OAuth2Response CodeResponse = null;

                if (result.Data.SessionID == SessionID)
                {
                    CodeResponse = await DropboxOAuth2Helper.ProcessCodeFlowAsync(result.Data.Code, AppKey, AppSecret, RedirectUri);


                    Settings.AccessToken = CodeResponse.AccessToken;
                    Settings.RefreshToken = CodeResponse.RefreshToken;

                    if (CodeResponse.ExpiresAt != null)
                    {
                        Settings.AccessTokenExpiry = (DateTime)CodeResponse.ExpiresAt;
                    }
                    else Settings.AccessTokenExpiry = DateTime.MinValue;

                    Settings.UID = CodeResponse.Uid;
                }
                else
                {
                    return "SessionID did not match the ID we submitted";
                }
            }
            catch (Exception e)
            {
                return e.Message;
            }

            return null;
        }

This is the code I am using to authenticate with Dropbox, maybe I am doing something wrong here?