ESP32-WROOM32D can't connect to MQTT broker

Hi,

First time trying openmqttgateway. I’ve flashed an ESP32-WROOM-32D with the esp32-dev firmware. It connects to the WiFi no problem but fails to make a connection to the MQTT broker, and I can’t work out why.

I’m using a HiveMQ Cloud broker, and I can connect to it fine using the mosquitto client using

mosquitto_sub -h instance.s1.eu.hivemq.cloud -p 8883 -u user -P 'password' -t '#'

so I know that the broker works and there’s no authentication step I’ve missed. The logs on openmqttgateway show only e.g.

W: MQTT not connected, aborting the publication
W: failure_number_mqtt: 2

I thought that perhaps verbose logging might help, but the MQTT connection is only attempted just after boot and the log level setting doesn’t persist across a reboot.

Given that the URL, port, username and password are correct, is there anything else obvious that I can try?

Thanks!