The API returned an error [NotFound | Xxxxxxxxx.] not_found - Not Found while uploading a file using creating admin client with JWTAuth

Hello, I am uploading a file using below code. But I am getting an exception from uploadAsync method as 

"The API returned an error [NotFound | Xxxxxxxxx.] not_found - Not Found"

var config = new BoxConfigBuilder(clientID
                                , clientSecret
                                , enterpriseID
                                , privateKey
                                , passphrase
                                , publicKeyID)
                .Build();
 
            var boxJWT = new BoxJWTAuth(config);
            var token = await boxJWT.AdminTokenAsync();
            var client = boxJWT.AdminClient(token);
  
            using (FileStream stream = new FileStream(file2ToUpload, FileMode.Open))
            {
                BoxFileRequest req = new BoxFileRequest()
                {
                    Name = $"Book2_{DateTime.Now.ToString("MM/dd/yyyy").Replace("/", "_")}.xlsx",
                    Parent = new BoxRequestEntity() { Id = folderID }
                };
 
                var newFile = await client.FilesManager.UploadAsync(req, stream);
            }

If I upload using developer token, it works fine.

What could be wrong?