'Internal traffic between two Google Cloud Compute instances not working

I want to enable internal traffic between two VM instances in the same VPC but block traffic from outside the VPC.

I've set up a new VPC network named vpc-dev.

In this network, I've created two VM instances with Ubuntu 20.04.

I've created a new rule for allowing internal traffic in this VPC with the instructions from google cloud docs: https://cloud.google.com/vpc/docs/firewalls.

But when I do - curl 10.0.3.9 -> I'm getting - curl: (7) Failed to connect to 10.0.3.9 port 80 after 0 ms: Connection refused

The configuration of the VPC for the selected region:

The VM instances:

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