M277dw stopped automatic duplex printing after Windows update

[Riojarina]

When I select double sided printing I now get a prompt for manual duplex.  I have reinstalled the software, still the same problem.   

[Andr-1611]

Hello @Riojarina,
Welcome to the HP Support Community!

Try this:

A) Printer settings Duplexer:
Search Windows for 'devices', and then click the Devices and Printers control panel setting in the results.

Right-click the icon for your printer model, and then
click Device Settings tab
Installable Options > Duplexer: installed

If not, change to installed.

B) Automatic Two-Sided Duplex Accessory:

Enter the Control Panel > Devices and Printers.
Right click the printer icon, then click Printer Properties.
Click the Device Settings tab.
Set the Automatic Two-Sided Duplex Accessory as installed and click OK to save the change.

Now Automatic Duplexing should become available.

Kind Regards
Andr-1611

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[Riojarina]

I had checked the duplex settings.   This happened on two HP Envy laptops (Windows 10) after the latest update.  What I hadn't noticed was that the default printer had been changed to HP Color Laserjet Pro MFP M277 Series FAX,  truncated to HP Color Laserjet Pro MFP M.. in the usual print dialogue.   Never happened before!

[Andr-1611]

During a reinstallation I found that the duplexer was not activated!
Did you also check if the toolbox is still working?