Receiving robot inactive alarm
If you are able to telnet the robot ip address on port 48000 and also able to telnet from robot to hub on port 48002 but still receive the alarm.
Check the controller logs and look for this type message
Controller: failed to send alive to hub UIMMON7hub(10.1.1.61) - communication error
But no firewall between Robot and Hub you can open the wireshark if windows or do a TCP dump at Linux to check the request from hub to robot and see the results if the robot don't reply the hub request.
When you have a busy server (have network request) and just one network card, some times the network is busy to reply the get alive from the hub and cause a communication error on the log and consequently a robot inactive alarm.
Any environment with a busy server with many network request.
Add a network card an configure one for management solution and the other card for a production environment, this way even if the production network card is busy the management network card will reply the hub request.