Unfortunately we could not reproduce your issue. We downloaded the OVA for Mautic 2.14.1.
Note that the password for the "bitnami" user in the terminal is "bitnami", due to not having logged in before we put an easy password for users, which they should change afterwards. That's why there is a script for changing the password right after logging in.
However, since we understand you're trying to access Mautic dashboard, in our case after entering the assigned IP (you can find yours with "sudo ifconfig"), http://192.168.254.50, we logged in as "user" with the password "6zXUz8R9vANW" (shown in "bitnami_credentials"), and we were able to log in successfully.