We have recently had several systems stop registering phones and receiving phone calls. After a lot of playing, we found it fixed instantly when turning off fail2ban. We have no banned IP's in the fail2ban list, so it shouldn't be doing anything even when it's on, but it seems to block all of Asterisk. Just disabling the asterisk section also makes it work.
This is now affecting systems that have been working for a long time. I hate to just leave fail2ban off.
