Question 1

Install fails or stalls?

Accepted Answer

Disconnect the USB cable, remove any partial OKI C3400 entry from Settings > Apps and Printers, stop the Print Spooler service, clear `C:WindowsSystem32spoolPRINTERS`, restart Spooler, then run the correct 32/64-bit package as administrator.

Question 2

Printer not detected?

Accepted Answer

Connect the C3400 directly to a rear USB port, not a hub; try a known-good cable; power the printer on before installation. Check Windows Device Manager for an unknown USB device or missing OKI port.

Question 3

Driver/version conflicts?

Accepted Answer

Uninstall older OKI C3400 drivers and duplicate print queues via Print Management, reboot, then install the latest package. Remove leftover ports and set the new queue as default.

OKI C3400 Driver