If you are running P103 or higher, you can reset it through the console connection after you power off and on. You will reset it to factory default, erasing the entire config including the password, but not the IP address. This is done through the bootup menu from the console.
If you have lower than P103, then you will need to contact Quintum directly to have the password reset.
You will need to reset the unit to factory default. This will erase the entire config and set the password to default (admin). You can only do this from console connection directly to DX.