Check ros master

Make sure the terminal you use to start the smach viewer is connected to your ros master. To check, run:

rostopic list

and look for topics of your state machine.

Check instrospection server

Your state machine needs to run an introspection server to allow the smach viewer to connect to it. A quick check is:

rostopic list | grep "smach/container_status"

If nothing is found, your state machine is not running an introspection server. See this tutorial for more details on how to run an introspection server.