First gateway and device

Hello everyone, I’m testing my first gateway and device.
Configuration: Raspberry Pi 3+B and Sx1276 connected to it.
Network server and applicati in server under the same home network but separate from Raspberry OS.
Gateway bridge, Network server and application server look installed correctly.
Gateway is ON on application server ( i see always few seconds ago in last seen when start the single_chan_pack_fwd in the raspberry with the recognition of the gateway and the sx1276 chip).
In the tab Live Lorawan Frames I don’t see anything.
The error in the log I see is:

connect got error unsupported packet type type 0×0 Module=mqtt and Connecting to TCP:// CONNACK was not CONN_ACCEPTED but rather Connection error module= mqtt

Do You know how to fix it?
Than you,