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I have a Brother HL-L2300D printer, connected by USB to a Raspberry Pi serving as a print server for a LAN segment somewhere. The Pi runs Raspbian, and has a samba server and a CUPS server running - the exact configuration of which I had forgotten about - and it was happily humming along for a couple of years, printing as requested.

Then about a week ago, users of several Windows 10 machines on the LAN started complaining about print failures. I was telling people to try removing the printer, then re-connecting to it (which in some cases seems to work for printers); but - they were unable to connect to the printer.

We checked that the printer itself works when directly connected one of those Windows boxes (via USB); and that, on the CUPS web interface, the printer is enabled and a test page prints correctly. The printer's CUPS management page says:

brother-hl-l2300d (Idle, Accepting Jobs, Shared, Server Default)

The error message people get when trying to connect the printer is:

Windows couldn't connect to the printer. Check the printer name and try again. If this is a network printer, make sure that the printer is turned on, and that the printer address is correct.

I should mention that \\1.2.3.4\ is browseable (where 1.2.3.4 is the print server's IP), and shows the printer. It's just the connection that fails.

My question: What could cause this failure, and what can I do to overcome it?

Additional information (ask if anything is missing):

  • I've tried uninstalling the Windows print driver for the printer, then adding a printer with the new driver. This gets me to the "Can't Connect" error before the dialog in which I can provide the new driver.
  • iptables --list on the Pi print server yields empty lists.
  • The version of Samba is: 4.5.16
  • The Raspbian version is 9.
  • When I try to Open rather than Connect to the printer, I get an Error 0x709.
  • cupsd.conf: here (pastebin.com)
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  • Check out support.microsoft.com/en-us/topic/… and see if this helps. Its related to that printnightmare vulnerability. You might have to set some settings and then tell those machines to trust the print servers IP or DNS name if that's what is going on. Do more googling on it too. Not sure if you are domain GPO environment or not but this might be what's going in so there you go just in case. Oct 30, 2021 at 13:06
  • Is the Pi using SMBv1? This Windows feature is disabled by default.
    – harrymc
    Oct 30, 2021 at 17:36
  • @harrymc: No, it's a fairly recent Raspbian. See edit.
    – einpoklum
    Oct 30, 2021 at 17:52
  • Did you check firewalls? What has changed - was Windows updated?
    – harrymc
    Oct 30, 2021 at 18:06
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    KB5006670 is the latest Window update to cause printer problems. Seems to fit the problem: "People whose systems have been negatively affected by the update report being unable to connect to network printers".
    – harrymc
    Oct 30, 2021 at 20:39

2 Answers 2

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tl;dr: Uninstall Windows updates KB5006670 and/or KB5005565.

(Credit to @harrymc for this answer.)

On October 12th, computers running Windows 10 received an automatic update from Microsoft, KB5006670. It has been reported that (emphasis mine):

The recently released ... update is just the latest in a long string of updates that have led to problems for Windows 10 users. People whose systems have been negatively affected by the update report being unable to connect to network printers while seeing 0x00000709 and Element not found errors.

See also an item on the BleepingComputer website's MS news channel:

New Windows 10 KB5006670 update breaks network printing

based on a long thread on their forum, with sysadmins ranting about this prob. In the future, you may want to consult that forum if you don't find an issue addressed here on SU.

This follows a similar problem last month, with Windows Update KB5005565, released September 14th.

In my case, the users' computers had the later update (6670). Uninstalling it allowed connecting to the network printer and printing seems to work (have not tried all machines yet).

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Summary of the above discussion:

On the face of it, a working setup suddenly stopped working, where the Windows 10 computers were suddenly unable to connect to the network printer.

After some verification, the only explanation left was Windows update, which is after all one of the greatest dangers for system stability.

The candidate updates were KB5005539 and KB5006670.

A search found the article KB5006670 is the latest Window update to cause printer problems, which said:

People whose systems have been negatively affected by the update report being unable to connect to network printers

The removal of KB5006670 did fix the problem and network connectivity was restored to the printers.

For hiding unwanted Windows updates, see the article How to Hide or Show Windows Updates in Windows 10, which also provides a download of the Microsoft Troubleshooter (which Microsoft does not provide any more).

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  • I see that on my PC KB5006670 was installed, but wusa resufes to delete it, saying, that no such update installed and indeed there is no such update. Are there any news on current failing update-number? I've opened linked forum discussion, but even KB5007253 is absent on my PC, nonetheless network printing fails.
    – PF4Public
    Dec 2, 2021 at 17:33

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