outgoingSMS Plugin: Sending with AWS SES

Hello,

I am able to send SMS messages using the following SNS server in Ireland:

sns.eu-west-1.amazonaws.com

However when I try to use the London region:

sns.eu-west-2.amazonaws.com

I receive an error:

Sender - InvalidClientTokenId - The security token included in the request is invalid

I have contacted AWS support and they said:

The error is likely due to invalid SigV4 request being signed: [1].

Make sure client region, User Credentials have access to publish API calls, instance clock is in sync with NTP, HTTP Method or any other request parameter is correct.

The developers will need to code the script to save to a log.

Is anyone able to advise what the issue might be please?

Thanks,

Greg