The Plesk Control Panel includes a security feature that automatically
locks users from logging in incorrectly multiple times within a
specified time frame.
By default this is set to 3 login failures within 3 minutes.
Should this happen you will need to login into your server as root, and run the command below
mysql -uadmin -p`cat /etc/psa/.psa.shadow` psa -e "delete from lockout"