Is possible install ispconfig again with no lose data?
No. And this wont help you as the ispconfig install is not the problem, the problem is the mysql login.
Take a look at the config.inc.php file from ispconfig, there you find the cleartext password of the ispconfig user (looks like an md5, but thats the claertext password). Now login to your mysql database as root user with e.g. phpmyadmin and make sure that the user ispconfig is able to login to mysql with this password from localhost. Change this only in mysql and do not change the password in any ispconfig file, you have to make the mysal login work with this password and not try to set any other password.