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Please be informed that, NX420 is not completely compatible with Mac OS X 10.10.5. The printer will work, however all other functions may not work with this operating system. Please try the following in order to get the printer work with your computer.
Please go to the link given below, download and install the update. Restart the computer after installing the update.
Note : Please make sure that you are installing the update after downloading it. It is a big file, so it may take some time to get it downloaded.
Then, follow the instructions given below.
Then, click the + (plus sign that you see on the print & scan window, and not on the keyboard) sign to add printer. Select your printer from the list.
Note : Make sure that you are resetting the printing system before adding the printer.
If the issue persists, or you have any questions, please be back and let me know.If you appreciate my service, please rate it EXCELLENT by clicking the EXCELLENT (5 Stars) and Submit. My goal is to provide you with excellent service – if you feel you have gotten anything less, please reply back, I am happy to address follow-up questions. Thank you for your business!Thank you!S H E F I N