HP M479fdw duplex settings gone missing

[BoMc]

I've had this HP M479fdw for 2 years. It has worked pretty much flawlessly. I use HP toner carts exclusively. Firmware is CLRWTRXXXN002.2539E.00.

In the last couple of weeks, the duplex settings disappeared. How do I get them back? 

Thanks.

[MacFixerX]

I’m facing the same issue: the duplex option has disappeared. I believe it happened after upgrading from the previous macOS version to 26.2. I’ve tried reinstalling multiple times using both the HP app and the basic Bonjour protocol, but neither method restores the duplex feature.

[MacFixerX]

After some trial and error, what worked was enabling the duplex setting by default in the printer’s web interface. Once I did that, macOS recognized the duplex option. 

[AnonMacUser]

Enabling the duplex option in Copy/Print settings in the web interface didn't fix it for me. This was broken for me on the latest Sequoia release in addition to Tahoe 26.2.

What did fix this for me: go to the the Printer's web interface, Network Tab, Advanced Settings, Bonjour in the left sidebar. Change Bonjour Service Name to "HP Color LaserJet Pro MFP M479fdw" from whatever it's set to (the latest HP firmware seems to default this to the wrong model string, which seems to convey the wrong feature set to the AirPrint driver configuration). After doing that, I re-added the printer on the Mac and it now shows a Duplex setting.