This I believe isn’t so much an Apple problem as it is printer related but here goes anyway. I have an HP Officejet 8040 printer that is fairly new which supports both regular print via wifi as well as AirPrint. Neither my iPad Air 2 nor iPhone 6+ can wake up the printer from sleep mode to cause it to print. However, I can print something with my wife’s Windows 10 laptop via wifi just fine and, if I get to it quickly, I can then print something with either I-device. In other words, once the printer has been woken from sleep mode by the Windows 10 laptop it can then be used by the iPad and iPhone till it goes back to sleep. Once the printer has entered sleep mode neither I-device will detect it. I’ve been through the printer settings and troubleshooting guide and found nothing wrong. Distance from I-devices to the printer is less than 10 feet. For whatever reason, neither I-device will wake the printer. I’m guessing this is a quirk with HP’s AirPrint comparability but I’m sure open to suggestions. Thanks!