Snips audio server: Unable to reconnect to the mqtt broker


I created a skill in italian language then I deployed it on a raspberry with a freshly installed os.
The problem is that the assistant works only on the first call then it does not work anymore.
It seems to be a problem relative to snips audio server because looking at logs (snips-audio-server -vvv) there are 3 lines with ERROR.
ERROR: rumqtt::client : snips-audio-server|1191-raspberry-1 Disconnected: (Error(SyncMpsc (Disconnected), State { next_error: None }))
ERROR: snips-audio-server: NoDevice
ERROR: snips_common_cli::cli : Unable to reconnect to the mqtt broker, ending the program.

I followed the installation process on raspberry and correctly configured both the speaker and the microphone.