Assuming that your printer supports AirPrint - and is set-up correctly and was working as expected prior to updating your devices to OS27 - should you continue to experience difficulties your WiFi Router may be unexpectedly dropping Apple Bonjour traffic on you local network - or your WiFi Router or Network Switch may be blocking this (or other) device discovery protocol(s).
This can occur for a number of reasons. Ensure that your wired and wireless network segments are part of the same IP-subnet, are not defined as separate VLANs - or that one or other are defined as “guest” networks, or placed in a DMZ. You may find that your router has a setting that limits/restricts broadcast and network discovery traffic; by example, if your Router has an IGMP Snooping setting, try toggling this or similar settings. Your Router WiFi settings may also have privacy settings that isolate WiFi clients from each other; if present, ensure these settings are disabled.
The Apple Bonjour protocol uses mDNS (Multicast DNS) UDP port 5353.
You may find that restart of your network components will resolve the problem. You’ll need to restart your network devices in the correct order. Assuming that you WiFi Router provides DNS services for your network, restart devices in this order - allowing time for devices to fully boot/restart prior to restarting other devices:
- WiFi Router
- Upstream wired Network Switch(es)
- WiFi Access Points / Network Extenders
- Other fixed infrastructure devices - such as Printers
- Client devices
If you continue to have difficulties, check to see if your devices are using the WiFi Private Address feature. This feature is intended to provide additional privacy and security when using “public” (untrusted) WiFi networks. For iPad and iPhone:
Settings > WiFi > [Your WiFi Network / SSID] - tap the “i” icon - Private Address
The Private Address feature is largely unnecessary for your home WiFi network; if enabled, Private Addressing can interfere with anticipated operation of other devices, such as AirPrint/Airplay. In such circumstances, you may need to disable this feature - and can be enabled or disabled for each individual network.
Use private Wi-Fi addresses in iOS 14, iPadOS 14, and watchOS 7 - Apple Support
If you have a VPN App or profiles installed, or a security/AV/firewall App such as Norton, these may be interfering with your iPad's network stack - sometimes impacting AirPrint/AirDrop and related services - even if the VPN connection is seemingly turned off.
If applicable, the resolution is usually simple; you may need to remove the Security App and/or VPN from the device - and then perform a forced restart. You might also try a reset of your iPad's network settings:
Settings > General > Transfer or Reset iPad > Reset > Reset Network Settings
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