I can't launch LoRa app server

ChirpStack Application Server
1

lora-app-server[5432]: time=“2018-04-26T15:41:22-05:00” level=error msg=“handler/mqtt: connecting to broker error, will retry in 2s: Identifier rejected”

sudo systemctl start lora-app-server

2

https://forum.loraserver.io/t/connecting-to-mqtt-broker-failed/440