If you see an error message near the Print button, saying the Printer is Offline you will not be able to print. The solution is to choose the printer setup you wish to use from the drop down menu as shown in the screen below.
If you have selected the Leitz Icon printer and you still see the error message saying Printer is Offline, Go to System Preferences/Control Panel and follow the steps to Add a new printer.
If you are planning to print to your Leitz Icon from both USB and Wi-Fi, add a printer for each and call it something like Leitz Icon USB and Leitz Icon Wi-Fi to differentiate the setups in the software. Make sure when you go to print that you choose the appropriate setup in the drop down list.
Once you have added the printer in System Preferences or Control Panel go back to the software and choose the printer from the dropdown list as show in the first screen/illustration. The print button will now be Green and you are ready to print.