I think this could be my fault, I’ve been trying to clean up a bunch of horrible old buggy code, but sometimes I’ve been a bit TOO enthusiastic about cleaning them up 
I’ll look at this now.
Edit, A few mins later: Nope, it seems fine to me:
I’m intrigued as to what the problem could be. The only thing that jumps out at me is that I moved it from the old-and-busted hooks to the new simple-and-secure hooks.
If you’re good with your shell, can you please do this, and paste the output:
[root@12-dev-cluster sysadmin]# cd /var/www/html/admin/modules/sysadmin/hooks
[root@12-dev-cluster hooks]# ./fail2ban-getbanned
[root@12-dev-cluster hooks]# cat /var/spool/asterisk/sysadmin/banned
{"_timestamp":1437973180,“SIP”:[“1.2.3.4/32”]}[root@12-dev-cluster hooks]#
[root@12-dev-cluster hooks]#
That part in bold is what should be visible in the GUI (formatted correctly, of course).
Preemptive warning: Don’t try to edit that file, as it’ll immediately stop working, and cause FreePBX to crash when it tries to run it. (This is me in my paranoid ‘someone is trying to hack your machine, and I’m just going to sit in the corner and cry’ response.)