Getting error:"Cannot read property 'split' of undefined" when using AWS auth on rest api

Hello! I've configured a REST api resource that I want to use AWS authentication with. However, when I attempt to make a call to an endpoint, I get the error:
error:"Cannot read property 'split' of undefined"
This does not occur when I send the request to an endpoint with no authentication.
In the Authentication section, I've populated the region, key, secret key, and left the service blank. Is there something I need to add?

Figured it out. This happens when the “AWS Service” field is not populated in the resource definition.