.net core – why Just one of two message is delivered in rabbitmq?

I am trying to connect two applications using RabbitMQ (EasyNetQ) together. I am using the Send/Receive pattern. So Application (A) will send a command to Application (B) and Application (B) will send the result after the process.

But just 50% of messages are always delivered to Application (B). This is my RabbitMQ Panel graph. As you can see, only the Message with the delivered graph (light blue) can be processed in Application (B) and the other is just consumed.

Should I change any configuration on my messages or my application connection to ensure all messages will be delivered?

It may be useful that I test My sender without any consumer and all the messages were received in my RabbitMQ but when I Ran my consumers all of my messages were deleted from the queue with out any process in my consumer service.