Invalid JSON payload when trying to verify amazon sns

Your software
My Mautic version is: 4.3.1
My PHP version is: 7.4.3
My Database type and version is: 10.3.34-MariaDB-0ubuntu0.20.04.1 - Ubuntu 20.04

Your problem
My problem is:
I cannot verify the sns connection to my mautic installation. Everytime I try this error is logged into the Mautic logs.
These errors are showing in the log:

[2022-06-24 04:02:15] mautic.ERROR: Uncaught PHP Exception Symfony\Component\HttpKernel\Exception\HttpException: "AmazonCallback: Invalid JSON Payload" at /var/www/clients/client1/web1/web/app/bundles/EmailBundle/Swiftmailer/Amazon/AmazonCallback.php line 53 {"exception":"[object] (Symfony\\Component\\HttpKernel\\Exception\\HttpException(code: 0): AmazonCallback: Invalid JSON Payload at /var/www/clients/client1/web1/web/app/bundles/EmailBundle/Swiftmailer/Amazon/AmazonCallback.php:53)"} {"hostname":"ubuntu-us-southeast","pid":290594}

Steps I have tried to fix the problem:

I have verified the json module is loaded in php.