Hello,
Let me explain my situation first, I've already successfully sent data to the losant web server using mqtt via the gateway with data from a mcModule 120 (it was very simple with great documentation), now my boss wants me to figure out how to send the same data to AWS,but from what I've found I can't directly publish the data due to the IOT certifications that AWS needs to accept data. I saw that you can use a pi as a "middleman" so to speak to receive the data from the gateway then publish it to AWS. I've installed mosquitto and the client runs ok (v3.1) on the pi but I do not know how to properly configure the gateway for this or what part of my code I should modify to make this work.

So has anyone been able to successfully do something similar or am I missing something obvious?.

Current code:
https://github.com/Bernstern/Safe-In-Home/blob/master/Safe_In_Home.mcScript

There were a couple of users that were discussing using Pi's as middle men - not sure the status of this.

Anyone out there that has done this that can help Bernstein?

As mcJohn mentioned, you can also forward the information to a service like CloudMQTT as an option. They do have a free tier and there are other ones out there as well. To help, you can check out this video that walks-through setting up CloudMQTT as a service. On this video we subscribe to the topic on an Android phone to view the data so not quite what you are looking to do but hopefully it helps a bit (CloudMQTT stuff starts around the 0:50 mark)

https://youtu.be/WfkQmg5P-3k