I can't be completely sure, but I guess something is going on with sierra and printing system in general? I tell this, as I had no problem to print when I was in el capitan, with my HP DESKJET 2540. Now, usually I can print, but when I go to photoshop CC 2015 and try to print, the photoshop quits! I can still print in Ms Word etc, but sometimes it stuck while printing. It is a rather new printer(2 y.o. model or something like this), so I guess it is not a not-supported old printer. And as I said I had no problems just a couple of months ago with el capitan. HP drivers page mention nothing special about sierra, but I found somewhere else an HP page saying that if the printer worked in el capitan, it should work in sierra too, after upgrading. Anyone having any idea why this happens?