Messages are not being removed from the queue

[carlosschroder-migrate]

I created an app based on the code of the example "amqp_consumer.c". My app is getting the messages, but the
Rabbit server's web client indicates that messages are not being removed after reading. A reading is required
through the web client, menu "Get Messages", so that they are removed. My Rabbit MQ server is version RabbitMQ 3.6.2, Erlang 18.3, I use a structure
of virtual host, exchange and queue.
The basic consume I'm calling like this:
amqp_basic_consume(conn, 1, queuename, amqp_empty_bytes, 0, 1, 0, amqp_empty_table);
I've already tried setting the no_ack parameter to 0 and calling the method to explicitly send the ack
amqp_basic_ack(conn, envelope.channel, envelope.delivery_tag, 0);
unsuccessful in "cleaning" messages from the queue. What could be wrong?