I didn't have time to check mDNS settings yet but in the meanwhile we encountered the same problem with a 7835i with the latest firmware. Everything about AirPrint and Connectivity setting is checked so maybe it's the same problem. We we'll check mDNS settings on the access point unless you found something different that could cause this problem... if so let me know please!
Hostname should not be an issue.
My guess would be that you have a router/gateway that does not allow mDNS going from wireless (iOS devices) to wired (CQ8900)
If airprint is enabled and configured, and you can actually view CWIS from your iOS device , you should be able to discover the printer.
I've done what you've suggested (checked settings and updated firmware) but still it doesn't work.
The only thing I've changed is the printer host name, maybe I have to set it as it was by default?
Could wifi channel transmission affect in some way?
Assuming Airprint is enabled, and you can get to the printers IP address in Safari, it should just work, asssuming it is setup properly.
Can't hurt to update the firmware though.
a CQ8900 with firmware 072.161.077.15201 and network controller 072.167.15201 has a lot of difficulties with AirPrint. The machine and the iPhones are all in the same network, we have already tried to reboot them together with the router but it doesn't appear as an AriPrint printer in the print dialog. Also with different iPhones but no way to make it work. Are there any known issues about it? What we can do? We have also tried to disable and then enable again AirPrint functionality but with no success. Is there something else we could check?
Thank you for your support.