How to solve Mac error -9923 when scanning over a network

Mac error -9923 can occur when scanning over a network, under some conditions. If it does, you might get a message saying “An error occurred when communicating with the scanner.” The result: you can’t scan.

The problem seems to pop up out of nowhere. And printing will continue to work. It’s only scanning that’s an issue. Weird.

If you do a Google search for this issue you will find many totally unhelpful tech “support” responses from HP and Epson (Canon is better). They tell you to uninstall drivers, reinstall drivers, turn the printer/scanner on, turn the printer/scanner off, restart the router, restart your Mac, restart the coffee pot. Total waste of time.

The real answer is in the network settings. You have a choice: adjust the printer’s network settings (harder, but it solves it for the whole office), or adjust your Mac’s settings (super easy, but it only solves the problem for you).

Solving the problem by adjusting the printer’s network settings amounts to turning OFF IPv6 on the printer. This is done various ways, depending on the printer. With some printers, you’ll see a panel on the front, and you’ll go to the Settings, and then Network (or maybe LAN settings), and eventually you will find a place to turn IPv6 off. With other printers, you’ll type the printer’s IP address into a browser, and that will give you control over the printer’s settings. Some printers come with their own Mac app, which you can use to adjust settings. Either way, it all comes down to one thing: you want to turn OFF IPv6 on your printer.

The easier way: fix it at the Mac end. Go to Apple menu / System Preferences / Network, then click the Advanced button.

Network preference pane
Network preference pane. Click “Advanced…” button.

After you click Advanced, click TCP/IP (at the top). Then change IPv6 to “Automatically.” Then click OK, then click Apply. Then close the System Preferences window.

Configure IPv6 Automatically
Setting IPv6 “Automatically” in Network preference pane

If IPv6 already said “Automatically” try changing it to Link-local, then clicking OK, then clicking Apply. Then go back in and change IPv6 to “Automatically” again.

If I were you, I’d try changing my Mac’s Network settings first. It’s easy, and easily undone. If it works, great– you’re done. If it doesn’t work, put things back the way they were, and then tackle the problem from the scanner/printer’s end, by changing the printer to disable IPv6.

As you can see, both methods try to match up the Mac’s network settings with the printer’s. In the first case, we change the printer’s settings so it matches the Mac’s. In the second case (the one I’m recommending), we’re changing the Mac’s setting to match the printer’s. Regardless of the method, the proof is in the scanning: if, after changing the Mac’s settings, you can scan, voilá! If you can’t scan, change the printer’s settings (in the printer itself). That should do it.

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19 thoughts on “How to solve Mac error -9923 when scanning over a network

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  1. Thanks so much for this! Fixed it!

    I also agree with your points about the official tech support suggestions – it’s always on the lines of uninstall drivers, reinstall, turn off, turn on, put your right foot in, put your right foot out, turn around and shake it all about, reboot the router, reboot your laptop, reboot your life, etc etc etc. A lot of work and rarely works.

  2. I was using Express VPN and I tried disconnecting from it and it reset it without doing anything else and then I turned VPN back on and it seems to have fixed it. Lets see how long that lasts.

  3. Thanks! Works perfectly. I just bought a new Canon printer and the scanner wouldn’t work. It was driving me nuts. If you have time, could you please explain why changing this setting will allow the printer to work?

    1. Basically, the “old” style of internet address was IPv4. Addresses look like this: abc.def.ghi.jkl

      That is, the address is in four parts. If you look in your network settings you will see something like this: maybe 192.168.1.x or 10.0.1.x.

      This is all very good if the printer has an address in the same family. And it would, except… somewhere along the way, a new standard for IP addresses (Internet Protocol addresses) was developed, because we (the world) were going to run out of unique IP addresses someday if the addresses were in the IPv4 format. You can see how that could happen.

      So… “they” came up with IPv6, because the addresses are way longer than IPv4 addresses, and therefore there are many times more unique addresses for us to use. Great stuff, except it came out of a committee (which is fine) but there were details that weren’t quite agreed upon, so every implementation of IPv6 networking could potentially be a little bit different, depending on the company that made the networking equipment or card in the device. (For that reason, it is often better to keep using IPv4, at least for the time being.) A lot of devices (including Macs) let you turn on both kinds of networking, and somehow the “right” kind of networking is grabbed and everything is great. Generally, what was grabbed was IPv4.

      For some reason, either scanning over a network is an IPv6 thing only, or your scanner insists on IPv6, so we just have to get our Macs to obtain an IPv6 address, so we can talk to it. It would work either way: tell the scanner to speak IPv4, or tell the Mac to speak IPv6.

      I hope that explains it.

  4. Hi Christian-

    This worked briefly (turning off IPv6 at the printer, Canon TS9120). Now it’s back to the 9923 error after I changed NOTHING. I’m about to throw my printer thru a wall. Any other suggestions? FWIW…I also tried to change the IPv6 address manually at the printer. No luck there either.

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