How can I tell if my app is working well?

I have an app hosted on and it has recently been publicized so now I am getting more users. I have it configured for 300 simultaneous users, but I have not seen more than 10 connections on my dashboard. However, sometimes when I check on the app as a user, I get the greyed-out app and "Disconnected from server" message.

Is there a way to know if I am up against any of the configured thresholds and if my users are having bad experiences? I am having a bad test experience, but there is no evidence of it in my dashboard or in the log.