1. Go to WHM (root) >> SQL Services >> MySQL Root Password.
2. Click generate password, please uncheck the symbols check box and click regenerate until the strength greater than or equal 80%
3. Click use password & change password.
4. Go to RVsitebuilder Installer and try to install it again.

Note: New database password should contain English characters both upper and lower case, and also at least one numeral.

Or, many times this problem occurs because the phpMyAdmin requires login. So, please go to WHM -> phpMyAdmin, login to it if required. Then go to RVsitebuilder to install database again.