You can enable debug for a specific CPE. Go to Admin → Config. Then click “new config”. For key enter cwmp.debug and value DeviceID.ID = "<YOUR_DEVICE_ID>"
The debug log will be where ever you have specified in the genieacs.env file. Here is my entry for example purposes only:
GENIEACS_DEBUG_FILE=/var/log/genieacs/genieacs-debug.yaml