Non-recoverable error

A colleague is having a hard time trying to connect to our server, it keeps saying non-recoverable error even after accepting all certificates and trying to disable hostname certificates.
Any idea on how to solve this?
Thank you.

You can try checking the logs for some relevant information at c/users/user/roaming/spark/logs/ there are a number of log files there, so check them all and look for recent entries.

It was an error related to the firewall, the port 5222 of the firewall was closed, solved thanks!