Just inherited a Phaser 6121 from a colleague who has upgraded. She has used it with no problems for a number of years.
I'm running Windows 10 x64. I've tried for hours to set it up as a printer on my laptop to no avail. I have got the scanner working.
I'm using a USB cable as I just want it as a local printer to my laptop. Have also tried with ethernet but no joy.
Have tried downloading drivers but nothing happening.
Install the driver and then plug it into the USB port on the PC.
Did you ever find a solution to this? I am having exactly the same problem with the 6121MFP.
The computer recognises the scanner/fax but doesn't recognise it as a printer.