Did you close the console that was running the H2 web console batch file?
You say PC, do you mean Windows? You should be able to connect to your own machine regardless of firewalls. If you had set up your SMTP server, you could have tried using the password reset provided through Mango. On Windows both IPv4 and IPv6 address work with the H2 web console....
If you have a JSON backup in your Mango/backup you could throw away the existing data and database and reimport it into a fresh installation by moving the Mango/databases directory while Mango is not running.
If you have an SQL backup in your Mango/backup from before your changed the password you could move the databases directory while Mango is not running and then restore this backup into a fresh installation.