This is not implemented in the software yet but it can be done. Ask for the error status via USB (if connected that way).Run the vendor software to print a label via the network (Ethernet/WiFi) and capture the network packets with tcpdump or Wireshark.bin file again and send it to the printer to see if that helps. You could comment out those function calls for example, create the. What you would want to modify are the setup commands. Run a modified version of brother_ql_create: Save the raw version of create.py into a folder on the Raspberry Pi 2, change it, and run this instead of brother_ql_create.I do not own the QL-720NW myself so I cannot debug it directly. Usually it's a problem with the commands in the raster protocol file sent, if such an error occurs. Quite a lot of problems in that error class. I assume the problem is the 1 second interval flashing. Red lamp flashes in 0.3 second intervals: The roll cover is opened (While running).

Red lamp flashes in 1.0 second intervals: The manual states this about a flashing red LED:

Brother ql 720nw label printer