If you see that the instance is not responding on the internal port this could mean a few things.

The first is that FusionReactor is not running, the second being that for some reason during start-up the port was unable to bind.

If you look at the Application Server log file, you will normally see a FusionReactor block that indicates FusionReactor is running (however Windows services can hide this).

In the Application Server log you will typically see:
INFO Fusionreactor: --------------------------------------------------------------------------------------
INFO Fusionreactor: FusionReactor - Copyright (C) Intergral GmbH. All Rights Reserved
INFO Fusionreactor: Revision:  8.4.0 fusionreactor.9174.312f374

You will also see in the instance directory that there is a fusionreactor.lock file existing, this file will only be in place if FusionReactor is running:

If a port for FusionReactor is already in use, you will see something similar to:
2020-09-07 09:25:29.956:WARN:oejuc.AbstractLifeCycle:FAILED SelectChannelConnector@ java.net.BindException: Address already in use
java.net.BindException: Address already in use

This indicates that for some reason the port for FusionReactor was already in use, maybe as the port never closed properly or multiple copies of FusionReactor are running with the same port.

In order to troubleshoot, we advise that you check the application server log and see if FusionReactor did indeed start and if you have any port binding issues.