It's difficult to say what is going on without logging into the ATLAS. Can you get a serial connection to either the from CRAFT port or the ADMIN port on the back of the controller module?
It's possible the unit factory defaulted, but if it did, the Ethernet port should still be active, just at the default IP of 10.0.0.1, so I believe logging in with a serial connection is your only option at this time. You can look at this guide for connecting to the CRAFT/ADMIN port: Connecting a Modem to the Control In, Chain In, or Craft Port of an ADTRAN Product
Thank you Patrick. Tried logging in via the Craft port but could not get connected. Had to build the cable and using MOBA xterm as the emulator.
You've probably lost the battery in the clock/calendar/NVRAM chip. Some of the 890s have a separate replaceable battery and some require unsoldering a chip on the motherboard. You really need to take the cover off and look to be sure. See this thread for details: https://supportforums.adtran.com/message/25060#25060