# Neptune Loader Errors
<a name="load-api-reference-load-errors"></a>

When an error occurs, a JSON object is returned in the `BODY` of the response. The `message` object contains a description of the error.

**Error Categories**
+ `Error 400`   –   Syntax errors return an HTTP `400` bad request error. The message describes the error.
+ `Error 500`   –   A valid request that cannot be processed returns an HTTP `500` internal server error. The message describes the error.

The following are possible error messages from the loader with a description of the error.

**Loader Error Messages**
+ `Couldn't find the AWS credential for iam_role_arn`  (HTTP 400)

  The credentials were not found. Verify the supplied credentials against the IAM console or AWS CLI output. Make sure that you have added the IAM role specified in `iamRoleArn` to the cluster.
+ `S3 bucket not found for source`  (HTTP 400)

  The S3 bucket does not exist. Check the name of the bucket.
+ `The source source-uri does not exist/not reachable`  (HTTP 400)

  No matching files were found in the S3 bucket.
+ `Unable to connect to S3 endpoint. Provided source = source-uri and region = aws-region`  (HTTP 500)

  Unable to connect to Amazon S3. Region must match the cluster Region. Ensure that you have a VPC endpoint. For information about creating a VPC endpoint, see [Creating an Amazon S3 VPC Endpoint](bulk-load-data.md#bulk-load-prereqs-s3).
+ `Bucket is not in provided Region (aws-region)`  (HTTP 400)

  The bucket must be in the same AWS Region as your Neptune DB instance.
+ `Unable to perform S3 list operation`  (HTTP 400)

  The IAM user or role provided does not have `List` permissions on the bucket or the folder. Check the policy or the access control list (ACL) on the bucket.
+ `Start new load operation not permitted on a read replica instance`  (HTTP 405)

  Loading is a write operation. Retry load on the read/write cluster endpoint.
+ `Failed to start load because of unknown error from S3`  (HTTP 500)

  Amazon S3 returned an unknown error. Contact [AWS Support](https://aws.amazon.com/premiumsupport/).
+ `Invalid S3 access key`  (HTTP 400)

  Access key is invalid. Check the provided credentials.
+ `Invalid S3 secret key`  (HTTP 400)

  Secret key is invalid. Check the provided credentials.
+ `Max concurrent load limit breached`  (HTTP 400)

  If a load request is submitted without `"queueRequest" : "TRUE"`, and a load job is currently running, the request will fail with this error.
+ `Failed to start new load for the source "source name". Max load task queue size limit breached. Limit is 64`  (HTTP 400)

  Neptune supports queuing up as many as 64 loader jobs at a time. If an additional load request is submitted to the queue when it already contains 64 jobs, the request fails with this message.