I have used Demo printers for years. In the past, their software was a bit quirky for Macs, but in recent times, seems to have improved. I would (1) download and install the latest software for the Dymo. (2) Go into the System Preferences app and click on Printers & Scanners. There you may have to reselect the printer to activate it. (3) Sometimes I have had to disconnect the printer's power to reset it. Leave the power off until the LED goes out which can take a minute or so. If this all fails, then I suggest going to Dymo's support site for help.