Hi Awais,
It seems to be that AWS changed the length of their Client ID. When you were running the app locally the unique client ID that was generated was short enough to be accepted. When you deployed to the cloud the ID was too long.
In order to fix this issue i made a pull request on the connector repo. I'll make sure this gets merged and updated to the appstore ASAP.
https://github.com/mendix/MxAwsIotConnector/pull/3
Regards
Simon