Can not see my gateway on application server

I installed gateway bridge, network server and application server on ubuntu and by these commands i checked services and they all are running and active:
systemctl status mosquitto
systemctl status chirpstack-gateway-bridge
systemctl status chirpstack-network-server
systemctl status chirpstack-application-server

I have raspberry pi 3 with ic880 shield gateway. I installed gateway OS base from
on my gateway. I configured gateway-bridge to send MQTT packets to my server. They are both on the same network and see each other. When I define gateway on the application server according to tutorials, the gateway last seen state is never. What configurations should I do in my gateway to send data to server.
I also installed gateway OS Full on my gateway and configured application server on the gateway but again the gateway last seen state is never. Please help me to solve this problem.