CSF is the first culprit if you are locked out of your own server firewall after too many failed login attempts from a certain IP.
The block was in your firewall, not cpHulk.
The IP was listed in /etc/csf/csf.deny and /var/lib/csf/csf.tempip and /var/lib/csf/csf.tempban
You can whitelist the IP in your firewall by placing the IP in /etc/csf/csf.conf, then running csf -r
Next you can place your external IP in the whitelist of cPHulk:
WHM > Security Center > cPHulk brute force protection > White/Black list > Quick Add your current external IP to: White List (Trusted IP List)
To find your external IP: