Maybe just a coincidence, and ADI-2 simply broke, so you need to send it in for repair.
Before, you could check if it’s just a PSU issue, which would save you from sending the whole unit in:
Did you notice the power connector that goes into ADI-2’s back has a “Turn-Lock”?
Manual page 7:
Socket for power connection. This socket supports locking type jacks as found on the included RME DC power supply. After inserting the connector carefully turn it by 90° so that it locks. If the unit turns off easily when moved then the connector is NOT fully inserted into the socket!
Look very closely:
No silver part of the plug may be visible, all silver hidden inside the socket, or the plug is not all-in, which might cause intermittent contact.
If this doesn’t help:
With a voltmeter or a car-voltage-check-lamp you can inspect if the PSU still delivers voltage.
https://www.amazon.de/Multimeter-Multim … NrPXRydWU=
https://www.amazon.de/Multimeter-Backli … s9dHJ1ZQ==
https://www.amazon.de/-/en/Motor-Vehicl … B00CIUWX0U