Please consult customer support before applying this following solution, it may cause Plesk failed to load.
If this following command failed
You should try this following solution:
mysql -uadmin -p `cat /etc/psa/.psa.shadow`
1.Load MySQL with the 'skip-grant-tables' option by adding skip-grant-tables into [mysqld] section of the /etc/my.cnf file
2.Restart MySQL with the command line below:
3.Repair password with the command line below:
# /etc/init.d/mysqld restart
4.Remove skip-grant-tables option from /etc/my.cnf
# /usr/bin/mysql -D mysql -e"update user set password=PASSWORD('`cat /etc/psa/.psa.shadow`') where User='admin';"
If the solution above still not working, I recommend that you contact Customer Support.