It is great that you are interested in HiveMQ and MQTT !
Your format seems correct, given that you are using username, password and hostname of your free HiveMQ cloud broker and port 8883. In order to investigate the issue, we need some additional information from you:
What is specific error that you get from Helium?
Which steps would I take to reproduce your issue?
Does Helium Console require a server CA in order to connect with TLS? If so, you can download the root certificate here .
This will create a file called “isrgrootx1.pem”, which you can use as “Server Certiciate”.