Pub/Sub mechanism is not working on 5.91 version of Signal Server

[GitHub-Ram]

I am not able to receive message from server to the app client while app web socket is connected.
In process app is able to send request with path
path: "v1/message/{destination}" and response 200 is received from server.

It is expected that destination will receive message on path : "api/v1/message" but this is not received, while socket connection is live.

If I disconnect socket either by restarting server or app client, when socket connection is stablished back, path : "api/v1/message" is received by the destination and sender both.

Signal has used Pub/Sub mechanism to enqueue message and dequeue to subscriber.
I am not able to understand this concept but did all as provide by @madeindra manual.
I think there is some problems with Redis DB or dynamodb configuration.
Please help me establish the communications between the client.