Are your disconnects purposeful? The disconnection reason is a connection timeout, meaning the client terminates due to the server not responding for some specified amount of time.
It's really difficult to say why after disconnect and reconnect, the sensor would stop sending notifications. But traces from the wiced_sense device would help you to debug it to see why it's not responding.
hello_sensor and hello_client were designed to work together. I recommend that you instead switch from wiced_sense to hello_sensor as the peripheral device. These will work together without changes and you can make your changes from there i.e. adding sensor readings etc.