Thanks for the kind words!
Since I'm not positive on your entire setup, you might find this Postman collection I just wrote helpful for troubleshooting.
It will basically allow you to simulate a Meraki GET and POST request to your AWS server or any other for that matter. Just update the Endpoint address (i.e. localhost:1880) to your instance. I use this all the time while developing on an airplane 😉
https://documenter.getpostman.com/view/897512/71FUpux
First test with the GET request, to see if AWS return your validator key
Then, test with one of the POST requests to send an observation set.
Look into your AWS Cloud Watch logs to see if you get any helpful info.
The AWS permissions are somewhat complicated to get right.
Also, double check your Lambda Trigger settings.
(Here is an example test setup)
Good luck and let us know what you find out.
Cory