How can i enable communication between two tasks running on different AWS ECS Clusters

Question

I have two fargate tasks running in two different clusters, the first one is running on port 3000 and can receive requests from anyone, the second one is running on port 8080 and can be accessed only by the first one. Both are in the same Security Group and VPC.

I created an inbound rule to allow public access for the first one, then I tried to create other inbound rule to enable the access for the second through security group ingress. But when the first service tries to access the second, I receive an Timeout Error.

When I allow the public access to the second service, the communication works properly, but I cannot allow it for forever.

Each service has a loadbalancer configured, but I already tried to access the service by his task public ip without success too.

Anyone has any idea what I am doing wrong?? The inbound rules for the security group can be checked in this image