Error when trying test email

I am getting the following error using exact same region and credentials as working elsewhere.

Error executing "SendEmail" on "https://email.eu-west-2.amazonaws.com/v2/email/outbound-emails"; AWS HTTP error: Client error: POST https://email.eu-west-2.amazonaws.com/v2/email/outbound-emails resulted in a 403 Forbidden response: {"message":"The request signature we calculated does not match the signature you provided. Check your AWS Secret Access (truncated...) InvalidSignatureException (client): The request signature we calculated does not match the signature you provided. Check your AWS Secret Access Key and signing method. Consult the service documentation for details. - {"message":"The request signature we calculated does not match the signature you provided. Check your AWS Secret Access Key and signing method. Consult the service documentation for details."}