You people really don't know your own product nor understand the questions. The "**bleep**" printer will not wake up after going to sleep. The only way is to unplug the power and then plug it back in to reinitialize the printer. I have installed it using wireless and usb with the same problem. The printer "Envy 4500" is obviously a piece of "Junk". I will never buy another HP product. This printer is the second one withing two weeks and I will be changing brands to "Epson". They don't have this problem. You might even do better if you had some tech support in the United States of America!!!!!!!!!!!!!!!!!!!!!!!!!!!
Currently running a M127fw and a LaserjetPro 7500 under OS X. Every moring I have to cycle the power to wake the printer. No problems with the 7500 - the newest printer, but I have had this problem with 3 other HP printers - all different models. Same fix for each - either cycle the power or with the older printers you have to unplug the power supply and then replug.
btw - I can access the scan function of both MF printers using the Preferences Panel in OS X, even though HP says it is only available under Windows.