This worked for me on Centos. Follow the 8 steps below and you should be good to go.
Stop DenyHosts
# services denyhosts stop
Remove the IP address from /etc/hosts.deny
Edit /var/lib/denyhosts/hosts and remove the lines containing the IP address. Save the file.
Edit /var/lib/denyhosts/hosts-restricted and remove the lines containing the IP address. Save the file.
Edit /var/lib/denyhosts/hosts-root and remove the lines containing the IP address. Save the file.
Edit /var/lib/denyhosts/hosts-valid and remove the lines containing the IP address. Save the file.
Edit /var/lib/denyhosts/users-hosts and remove the lines containing the IP address. Save the file.
(optional) Consider adding the IP address to /var/lib/denyhosts/allowed-hosts
Start DenyHosts
# services denyhosts start