if i was you,
disable and remove, iptables and firewall and fail2ban, reboot server
i have experience with all control panel, for exam ispconfig,cpanel,...
all of theme have issue with firewall and iptables

but if you need firewall and iptables and cant live without it, you should install fail2ban
i told you earlier , the only way , install fail2ban, install firewall, and restart every thing
if fail2ban work fine, you never get error again
try just installing and configuring correctly fail2ban, not remove it

sorry for my bad english ,be happy

no, please don't disable service or delete service manualy
never change config manually , because ajenti will overwrite it ,
i looked in into your error log, there is nothing wrong with firewall, you should fix fail2ban
install fal2ban correctly , and restart , fail2ban & firewall & ajenti service
then click on firewall tab , if you get error again , tell me

sorry for my bad english ,be happy

I cant help you with ubuntu,
but you shoud check fail2ban and fail2ban-courierauth services
fix them and restart them, then restart firewall ,then ajenti
sorry for my bad english

what os do you use?

Munin dependency is 79 package , and it base on httpd, apache web server
so its not good idead , i need something simple in the ajenti control panel

yeah dns will not help

use reverse proxy

Я не понимаю вопроса и означает
Пожалуйста, объясните более четко

извините за мой плохой русский, быть счастливым

you said , you turnd of ssl
so when you turn of ssl , you cant acces with https:// ,try http://
with ssl on use https://
with ssl of use http://

sorry for my bad english, be happy

i dont know any thing about ubuntu,but in centos 7 you shoud
1,clean your meta

yum clean metadata

2,install latest version of rpm

wget http://repo.ajenti.org/ajenti-repo-1.0-1.noarch.rpm rpm -i ajenti-repo-1.0-1.noarch.rpm

3, update all package

yum update
yum upgrade

4,install ajenti and restart it

yum install ajenti
systemctl restart ajenti

sorry for my bad english , be happy