Review your printer setup:
Please ensure you have set up the printer according to these steps.
Re-enter the IP address of your computer with the QZ tray installed displayed in https://demo.qz.io/ as explained here in step 6.
If you still can't print:
Verify that the computer or server running QZ Tray and the device running PULPO WMS Android App are in the same network.
Ensure that there is no block of data transfers within your network.
Try to select a different printer or a PDF printer. Using a PDF printer, the label should be printed locally on the computer or server running QZ Tray.