Hello @jmmckean ,
Thank you for the outreach, and for the interest in MQTT!
One of the first areas that we recommend verifying when seeing connection failures with HiveMQ Cloud is to ensure that the TLS/SSL configuration is properly set for the connecting client. HiveMQ Cloud utilizes Let’s Encrypt certificates, which may need to be supplied directly to the connecting client for TLS/SSL authentication. The certificate itself can be obtained from our Frequently Asked Questions section here, or directly downloaded from this link.
Additionally, I would like to see if it possible to provide the configuration details for the connecting client, or the connection implementation itself if available.
Best,
Aaron from the HiveMQ Team