Cannot login to WHM?
ssh to the server and run:

# /usr/local/cpanel/etc/init/stopcphulkd

This will stop until chksrvd starts it back up again within 8 minutes.

To start

# /usr/local/cpanel/etc/init/startcphulkd

Disable cPhulk

# /usr/local/cpanel/bin/cphulk_pam_ctl --disable

Resource: https://documentation.cpanel.net/display/ALD/cPHulk+Brute+Force+Protection#cPHulkBruteForceProtection-FailedLogins