RAK7268 can't connct to chirpstack

why i can’t connect successfully and even can’t find my device

Are you using Chirpstack V4?

You selected MQTT for Chirpstack 3.x that will not work with CS V4.

You gateway is running WisGate OS V1, that doesn’t have MQTT for Chirpstack V4. You need to connect with Semtech UDP forwarder.

Standard port is 1700.

Yes,I’m using Chirpstack V4.
I follow your steps but still can’t connect

should i change the channel or what?

Depends on your setup in Chirpstack. But if you do not see your gateway in Chirpstack, then there is something else wrong. A different channel has nothing to do with the connection to Chirpstack.
Double check the URL to the chirpstack server in your gateway settings.
Make sure your Chirpstack server can be reached, I see an error Network is unreachable in the gateway logs.