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Lately my Mac cannot connect to any scanners. I get this error message every time I open the system scan tool on any of the connected scanners:

Failed to open a connection to the device (-21345)

I've tried removing all scanners and re-installing.

I've tried doing "reset print system" on each connected device and then rebooting my system.

I've tried buying a brand new scanner (HP Deskjet 2755e in this case) but that new scanner has the same issue.

Tried updating to Mac OS 11.6 Big Sur.

This is the 2nd Mac I've had that is affected by this and so far the only thing that has ever (temporarily) fixed it is wiping the entire thing and reinstalling my system. I shouldn't have to do this every time I get this error.

All the scanners are connected over Bonjour AirPrint.

How do I fix this?

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  • Having this problem with a Brother all-in-one on macOS Monterey. It was fine when I first got the new iMac a few months back, then Image Capture would pick it up if I ended and restarted the app; today it wouldn't pick it up until I power-cycled the scanner itself. I don't think it's a connectivity issue; printing to the device works without any issues whatsoever.
    – Alger
    Jun 23, 2022 at 15:05
  • I had similar issues with a Canon scanner. Finally I disabled the firewall on the Mac which made scanning possible. Interestingly enough it kept working even after I reenabled the firewall again. Computers, they are just magic.
    – nohillside ♦
    Jul 16, 2022 at 14:39
  • I just encountered this same problem - inspired by @nohillside's observation I tried disabling the Perimeter81 VPN that I have to use for work (not just disconnect but also quit the app) and after re-opening Image Capture I was able to scan again. It's weird that it interferes with scanning but not printing.
    – Anentropic
    Sep 28, 2022 at 15:21

1 Answer 1

Reset to default
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This may be a matter that Apple keeps requiring more and more permissions. For now, at least, I have fixed this for my Brother all-in-one on Monterey by enabling full disk access.

I added Brother iPrint&Scan application to Settings → Privacy & Security -> Full Disk Access. It also required a hard reset of the printer (that is, pull out the power cord at both ends for 10 seconds).

It did not require a Mac reboot for me but if it starts failing again I may try that. After I got scan working again, I disabled Full Disk Access and scanning stopped working, so this may be the fix.

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