Hi and welcome to Digi forum.
If the device is new, it should have a unique password on the label. In this case you should be able to login using:
User name: root
Default password: The unique default password printed on the label
See also: https://www.digi.com/resources/documentation/digidocs/90000583/default.htm#reference/r_assumptions.htm%3FTocPath%3DConfigure%2520network%2520and%2520serial%2520ports%7C_____1
If you have still issues, please look at our support options here: https://www.digi.com/support.
Digi Tech Support team