For LoopMeeting to work it needs HTTPS (port 443) communication to the LoopBooking environment.
The Android panel also needs to synchronize time and date with an NTP server. The Android OS is by default set to synchronize towards a Google NTP server, so NTP (port 123) must be open towards internet to make sure time and date are correct. The panels can also be configured to synchronize towards a specific NTP server.