Hi - if you are simply trying to use your Windows MID server (within AWS) to discover other IP's in the AWS subnet, be sure to enable the AWS security groups (SG) to allow IP comm between MID and targets. By default AWS isn't going to allow traffic to flow, even on subnets you've defined in your VPC.
Example: on my AWS lab playground, I defined a Security Group that allows all internal (private IPs) to talk to teach other, on any port. Of course you can restrict it more, but for a lab test I've allowed all local private subnets and ports to freely communicate. Note - not PUBLIC IP's... just private subnets defined within the VPC. By allowing all private IPs & ports to communicate, it reduces some of the hassle in a lab setting but of course, in a real-world scenario you'd want to be much more restrictive.
You can see in the screenshot other SG rules too, but for what you've described, a single SG might suffice?
Note: This is NOT Discovering Cloud resources via cloud-based discovery. Rather, this example is just empowering traditional horizontal based discovery, but within the context aws-cloud-based subnets...
Does this help?
