Unable to load AWS credentials from any provider in the chain

I have my application running on EC2. Trying to access dynamoDB from my Java application. But for every operation, I get "Unable to load AWS credentials from any provider in the chain".

* I have added dynamoDB permissions in the IAM role that gets attached to EC2 instance
* And also configured EC2 to assume that role in trust relationship.

Code:
```try {
AWSCredentialsProvider provider = new DefaultAWSCredentialsProviderChain();
AWSCredentials credentials = provider.getCredentials();
if(credentials != null) {
LOG.info("Credentials Key: " + credentials.getAWSAccessKeyId());
LOG.info("Credentials secret: " + credentials.getAWSSecretKey());
}
} catch (Exception e) {
LOG.info("Exception in credentials cause:" + e.getCause() +";message: " + e.getMessage() +";stack: " +e.getStackTrace());
}
```
The getCredentials() line itself throws an Exception with message: "Unable to load AWS credentials from any provider in the chain".
If I do not try to get credentials here and pass it to the DynamoDB client:
```dynamoDBClient = builder.withEndpointConfiguration(new AwsClientBuilder.EndpointConfiguration(url, region.getName()))
.withClientConfiguration(clientConfig)
.build();```

Then it throws the same exception when I try to do any operation.

I tried setting up the proxy too:

```ClientConfiguration clientConfig = new ClientConfiguration();
clientConfig.setProxyHost("yyy");
clientConfig.setProxyPort(port);
clientConfig.setNonProxyHosts("xxx");
clientConfig.setProtocol(Protocol.HTTP);```

and then passing it while creating the client:

``` dynamoDBClient = builder.withEndpointConfiguration(new AwsClientBuilder.EndpointConfiguration(url, region.getName()))
.withCredentials(credentialProvider())
.withClientConfiguration(clientConfig)
.build();
```
But no success.

Can someone @here guide me what am I missing here?