Yes... this, from ZAOC confirms:
"there is no "internal" A/D->D/A connection in Drezno. The connection between these two halves is provided only by the ribbon cable. Drezno is shipped with the cable plugged both sides to it"
My guess is that the cable is missing or not seated properly!
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You need to break this connection to introduce Lipsk or other expanders ;)
Super cool module, one of the most innovative things to happen in Eurorack, well.... ever! I love mine!!