How do i know root cause of the issue when trying to connect appian and AWS S3

Hello Chaithra A R 
You're getting "Access Denied" error from S3. I would recommend to,
Verify credentials and bucket name. Review IAM policy for S3 actions (use IAM Policy Simulator).

This articles might help you.
https://docs.aws.amazon.com/AmazonS3/latest/userguide/troubleshoot-403-errors.html ,

https://docs.aws.amazon.com/IAM/latest/UserGuide/access_policies_testing-policies.html

My AI told me this, when shown your error message. Please use it with care as LLMs sometimes write nonsense.

The error message you're seeing indicates that your request to access an Amazon S3 (Simple Storage Service) resource was denied due to insufficient permissions. Here’s a breakdown of the error message:

- **Service**: Amazon S3
- **Status Code**: 403 (Forbidden)
- **Error Code**: AccessDenied
- **Request ID**: GEC4SADZ0V9EAXY5
- **S3 Extended Request ID**: K1xnNBqqSOyIRzaG4oVhOF5gl445LMP0PhElTnz4pVJ8vb0ERbzMeoYFuJgwzGAzQMzss4FCqM8=
- **Proxy**: null

### Possible Causes and Solutions

1. **Insufficient Permissions**:
   - **Cause**: The AWS Identity and Access Management (IAM) user or role making the request does not have the necessary permissions to access the S3 resource.
   - **Solution**: Ensure that the IAM user or role has the appropriate permissions. You can attach a policy that grants the necessary permissions. For example:
     ```json
     {
       "Version": "2012-10-17",
       "Statement": [
         {
           "Effect": "Allow",
           "Action": "s3:GetObject",
           "Resource": "arn:aws:s3:::your-bucket-name/your-object-key"
         }
       ]
     }
     ```

2. **Bucket Policy Restrictions**:
   - **Cause**: The S3 bucket policy might be restricting access.
   - **Solution**: Check the bucket policy to ensure it allows access to the IAM user or role. For example:
     ```json
     {
       "Version": "2012-10-17",
       "Statement": [
         {
           "Effect": "Allow",
           "Principal": {
             "AWS": "arn:aws:iam::account-id:user/username"
           },
           "Action": "s3:GetObject",
           "Resource": "arn:aws:s3:::your-bucket-name/your-object-key"
         }
       ]
     }
     ```

3. **Object-Level Permissions**:
   - **Cause**: The object itself might have an ACL (Access Control List) that denies access.
   - **Solution**: Check the ACL of the object to ensure it grants the necessary permissions.

4. **MFA (Multi-Factor Authentication)**:
   - **Cause**: If the bucket policy requires MFA, the request must include valid MFA authentication.
   - **Solution**: Ensure that the request includes MFA authentication if required.

5. **VPC Endpoint Policies**:
   - **Cause**: If you are accessing the S3 bucket through a VPC endpoint, the endpoint policy might be restricting access.
   - **Solution**: Check the VPC endpoint policy to ensure it allows the necessary actions.

### Steps to Troubleshoot

1. **Verify IAM Policies**:
   - Check the IAM policies attached to the user or role making the request.
   - Ensure the policies grant the necessary S3 permissions.

2. **Check Bucket Policy**:
   - Review the bucket policy to ensure it allows access to the user or role.

3. **Review Object ACLs**:
   - Check the ACLs of the specific object you are trying to access.

4. **Examine VPC Endpoint Policies**:
   - If applicable, review the VPC endpoint policies.

5. **Use AWS CLI for Testing**:
   - Use the AWS CLI to test access and get more detailed error messages.
     ```sh
     aws s3 cp s3://your-bucket-name/your-object-key .
     ```

By systematically checking these areas, you should be able to identify and resolve the access issue.

Thank you for your inputs Stefan Helzle . In continuation to the above we have MFA enabled in AWS environment. Considering this and above mentioned scenarios do we have to establish any setup from Appian side.

I am not sure it is clever to configure MFA. I assume you want to use a service account to perform the actual calls, MFA will probably not work.

Said that, I am not a AWS or S3 expert and my naive next step would be to just test this.