Please, just to try this:
1) Reduce "bantime" to 600 seconds.
2) Comment out with a # the line "action" in jail.conf, and add a line "port = http,https"
With iptables --list you must see after fail2ban restart as following:
fail2ban-pma tcp -- anywhere anywhere multiport dports http,https
fail2ban-pma tcp -- anywhere anywhere
3) You have a duplicated "maxretry", delete one.
4) restart fail2ban, and try to access a few times the website using this line:
You should get banned (because regex is working perfectly as you tested).
Logged in by ssh, when you get banned, use iptables --list again, and your ip must be listed in the following chain:
Chain fail2ban-pma (1 references)
target prot opt source destination
RETURN all -- anywhere anywhere
Is not working and you are not banned, check the log file that fail2ban is using, and see if your attempt to enter to /phpmanager was logged correctly, and post line here.
To be debanned, you just have to restart fail2ban.
Post results pls.