How do I connect concurrently to Photon Chat?

My Chat clients (server-A and server-B) are running on AWS EC2 instances with Elastic Load Balancer.
My clients are connecting to Photon Chat concurrently.
I use Photon .NET Client SDK(v4.0.5).
My clients have a connection pool of Photon Chat. The connections use same userId and they are always connected Photon Chat.

But a client of server-A was disconnected frequently from Photon Chat. The cause when disconnected was None.
How do I connect concurrently to Photon Chat?

Answers