How to unlock an account if it is locked by Plesk because of wrong password was entered more than three times?
Plesk includes a security feature for the interface that locks users from logging in incorrectly multiple times within a specified time frame. (3 times in 3 minutes by default)
To unlock the interface use the following command as root in the system.
# MYSQL_PWD=`cat /etc/psa/.psa.shadow` mysql -u admin psa -e "delete from lockout"