Couple of suggestions
1. Make sure your firewall is open for Firefly. If you are running on a LAN just turn off the firewall and try it, if it works turn off the firewall and try again. If it fails time to look closer at the firewall.
failing that…
2. Go to the firefly.conf file and change the Log level to 5 or higher if necessary and restart – Look at the log try and work out where the problem is, if you get nowhere post the log back here
Good luck