Box .NET api

I'm created a simple command-line app in .NET to upload a file to a Box.com folder.  There does not seem to be ANY documentation on how to use the .NET API - just a couple of too-simplistic sample apps.  The app works fine if I login to the server and run it from a command prompt.  When I add the command to a SQL Server stored procedure, I get the following error: Exception creating BoxClient: {"error":"invalid_grant","error_description":"Current date\/time MUST be before the expiration date\/time listed in the 'exp' claim"}

Here is the code I cobbled together from the .NET samples:

        static void Main(string[] args)
        {
            try
            {
                Task t = MainAsync(args);
                t.Wait();
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.InnerException.Message);
            }
        }

        private static async Task MainAsync(string[] args)
        {
            string boxUser = args[0];
            string boxPath = args[1];
            string filePath = args[2];

            IBoxConfig boxConfig;
            try
            {
                boxConfig = new BoxConfig(CLIENT_ID, CLIENT_SECRET, ENTERPRISE_ID, PRIVATE_KEY, JWT_PRIVATE_KEY_PASSWORD, JWT_PUBLIC_KEY_ID);
            }
            catch(Exception ex)
            {
                if (ex.InnerException != null)
                    throw new Exception("Exception creating BoxConfig: " + ex.InnerException.Message, ex.InnerException);
                else
                    throw new Exception("Exception creating BoxConfig: " + ex.Message, ex);
            }

            BoxJWTAuth boxJWT;
            try
            {
                boxJWT = new BoxJWTAuth(boxConfig);
            }
            catch (Exception ex)
            {
                if (ex.InnerException != null)
                    throw new Exception("Exception creating BoxJWTAuth: " + ex.InnerException.Message, ex.InnerException);
                else
                    throw new Exception("Exception creating BoxJWTAuth: " + ex.Message, ex);
            }


            string userToken = boxJWT.UserToken(boxUser);
            BoxClient userClient;
            try
            {
                userClient = boxJWT.UserClient(userToken, boxUser);
            }
            catch (Exception ex)
            {
                if (ex.InnerException != null)
                    throw new Exception("Exception creating BoxClient: " + ex.InnerException.Message, ex.InnerException);
                else
                    throw new Exception("Exception creating BoxClient: " + ex.Message, ex);
            }

            try
            {
                await UploadFile(boxPath, filePath, userClient);
            }
            catch (Exception ex)
            {
                if (ex.InnerException != null)
                    throw new Exception("Exception Uploading File: " + ex.InnerException.Message, ex.InnerException);
                else
                    throw new Exception("Exception Uploading File: " + ex.Message, ex);
            }
        }

        private static async Task UploadFile(string boxPath, string filePath, BoxClient userClient)
        {
            var boxFolderId = await FindBoxFolderId(userClient, boxPath);
            using (FileStream fs = File.Open(filePath, FileMode.Open, FileAccess.Read))
            {
                // Create request object with name and parent folder the file should be uploaded to
                BoxFileRequest request = new BoxFileRequest()
                {
                    Name = Path.GetFileName(filePath),
                    Parent = new BoxRequestEntity() { Id = boxFolderId }
                };
                await userClient.FilesManager.UploadAsync(request, fs);
            }
        }

        private static async Task FindBoxFolderId(BoxClient client, string path)
        {
            var folderNames = path.Split('/');
            folderNames = folderNames.Where((f) => !String.IsNullOrEmpty(f)).ToArray(); //get rid of leading empty entry in case of leading slash

            var currFolderId = "0"; //the root folder is always "0"
            foreach (string folderName in folderNames)
            {
                var folderInfo = await client.FoldersManager.GetInformationAsync(currFolderId);
                var foundFolder = folderInfo.ItemCollection.Entries.OfType().First((f) => f.Name == folderName);
                currFolderId = foundFolder.Id;
            }

            return currFolderId;
        }