Hi !
Yesterday, around 11 p.m UTC, the server had to be restarted. There was an issue with apache2. This is why you got an empty list (by the way if you had refreshed the fgcom status page, you should had get a 404 error).
When the apache2 service has correctly started, users list has not been refreshed. This is why today, you have seen a big list of non-connected users.
And the Asterisk service (fgcom service), is very long to start up at boot (it is hosted on a very low-end machine). Maybe 30 minutes to add all the frequencies of FlightGear.
Sometimes, servers need to be restarted to fix issues, and I don't see how to prevent such a situation later. Maybe, be more rigorous?
Now, everything should work.
What I can do, is to improve the program responsible of the managing of the users list. This script has several problems and I must find the time to solve them.