The Object Key property value should not start with "/".
The Credentials File property allows the user to specify the path to a file containing the AWS access key and secret key. The contents of the file should be in the following format:
[default] accessKey=<access key> secretKey=<security key>
Make sure the credentials file is readable by the NiFi service user.
When using the Credential File property, ensure that there are no values for the Access Key and Secret Key properties. The Value column should read "No value set" for both. Note: Do not check "Set empty string" for either as the empty string is considered a set value.