[Trygve]

I have an Airport Base Station and an Airport Express. On the Airport Express USB is an HP M2727nf multi-function printer. I can print to it wirelessly from any device on the network, but I can't scan. The HP setup does not see it (although the Printer Pref Pane from System Preferences obviously sees it ok).

How can I scan from this network device?

[Cold Warrior]

Most printers can't scan over USB network share. Does this printer have an ethernet port?

[Trygve]

Yes, I believe it does.

[Cold Warrior]

Try plugging it into a free ethernet LAN port on the base station. Try the software there (you may need to set up your printer for ethernet sharing/access). Generally this is how scanning over a network happens -- ethernet not USB.