Once your platform is up and running it is very unusual for problems to occur with the software, however if they do there are a couple of places to start.
Firstly by looking at the log files referenced in Logging to try and diagnose where the error has occured.
You can also run build-config if required, to double check that the configuration of the system is correct, as this will auto detect any low level configuration issues when it runs.
For troubleshooting issues with nodes, read Troubleshooting node networking problems.
Finally if neither of these solutions are effective, you can use the Remote Support service to send Flexiant engineers a configuration bundle, and allow us to login to your installation remotely to help diagnose the problem (if you have a support contract with us)