Are you able to reach RUTX08 with RMS access functionality? (SSH / WebUI).
Have you added the PLC to the device access list?
You can also just port forward from your device to the PLC and then use RMS generated WebUI link to access that port.
If you're still having troubles - please send me your serial number of the device that is registered on RMS and add your device password. Send this information via private message to me.