AirPrint Works on Mac but not iOS

We have 4 Konica BizHub printers in our office, which state they are AirPrint compatible. I can print from my mac to the Konica via AirPrint without issue, but on my iOS devices (multiple iPads and my iPhone) the Konicas are not listed in the list of available AirPrint printers. We have a couple of ink jet printers that do show up on the mac and iPads, so all devices are on the right network. Any ideas would be appreciated. Thanks!