print from iphone
Make sure it’s compatible with Bonjour on your network
Install "Bonjour Browser" app for your iPad and iPhone as below link
Bonjour Browser
It's a free tool that browses Bonjour services on the network.
Tap "IPP (Internet Printing Protocol)" and you should see printers that O'Print enabled printers on the network.
If you don't see any printers on app, there is a problem with your network : It’s NOT COMPATIBLE with Bonjour.  

Your router must support Bonjour and Multicast.
- Update firmware of your router
- Make sure Bonjour/Multicast is Enabled/Allowed on your router. This is often found under advanced settings on your router control panel.
Unsure how to access your router settings... please contact your Router Company Support. (more about router settings)

1) Make sure all device are connected to the same local network.
2) Try rebooting device. 
3) Update your iOS. 
4) Check "printer properties" >> "port" tab >> uncheck " Bi-Directional Support"