Hello Michal,
As I mentioned in my first post, update the firmware to the latest version would be great to get rid of any SSL/TLS bug implementation on this device.
The last response error code changed +QMTOPEN: 0,-1
I have made some tests using Paho Python MQTT client and I’m able to connect to my HiveMQ Cloud instance, so I’m discarding the possibility of something wrong with these certificates files.
In theory you should be able to connect just by upload the trusted CA certificate (cacert.pem) to the modem module.
You can also give a try by querying the DNS server configured on this device and check if you are able to convert HiveMQ Cloud domain name to IP address.
AT+QIDNSGIP=1,“9d52b5d026654fc4b6057be2b55bc5f1.s2.eu.hivemq.cloud”
Other than that I’m running out of ideas. You can also reach out to Quectel support and try to get some help Technical Support | Quectel
Best regards,
Diego from HiveMQ Team