We have six or seven USB-attached MF4690s in our office that alll worked great on Windows 7 Pro and promptly stopped working after in-place upgrades to Windows 10 Pro this past weekend. (All were x64 except one 32-bit.)
Every single one had an older version of MF Toolbox and the scanner+printer drivers from the same time. We think the versions were v12 for most if not all of them.
MF Toolbox continued to run, but it could not contact the scanner and would not produce an error message--it would just hang until Task Manager was used to kill it. Printing continued to work without trouble.
We found this thread and a mix of various voodoo solutions worked on all of our PCs but one--notes on that one later.
First, a few observations.
1) The scanner driver seems to be independent of MF Toolbox in that it was possible to run MF Toolbox without trouble while the scanner driver refused to respond. It was also possible to run the scanner driver properly without MF Toolbox installed (we used Windows Fax and Scan to verify).
2) The easiest way to predict whether the scanner driver was/is working is to go to Devices and Printers, right click on the Canon MF device, and choose Scanner Properties. It would pop up a UAC dialog--after pressing Yes, if the Scanner Properties page actually opened, then all scanning would work. If it did not open, then it no scanning would work.
3) From what we can tell, all the problems in our case were caused by the files from the older driver and older MF Toolbox staying behind even after installing the latest v18 MF Toolbox and drivers from the current day.
Okay, here is the procedure that worked for us:
1) Go to Devices and Printers, right-click on the Canon MF driver and choose Scanner Properties. Click Yes on the UAC dialog. If the Scanner Properties window pops up, skip to step 10 below.
2) Right-click on the Canon MF device and choose Remove Device.
3) Unplug the USB cable.
3) Uninstall the Canon MF device driver software from Programs and Features.
4) Delete the MF4600 folder from C:\Windows\twain_32.
5) Reboot.
6) Install the latest Canon MF device driver software.
7) Open the C:\Windows\twain_32 folder in File Explorer and Devices and Printers to watch what happens.
😎 Plug in the USB cable and watch the driver auto-install.
9) Try step 1 again. If it works, continue. If not, then see the next section.
10) Test with Windows Fax and Scan. It should work immediately.
11) Uninstall Canon MF Toolbox if it is old (using Programs and Features).
12) Install latest version of Canon MF Toolbox (v18 as of this date). Rebooting and safe mode were not necessary for us.
13) Test scannng using Canon MF Toolbox.
14) Reboot and make sure it still all works.
Next section: the one holdout PC.
We did have one PC that refused to work no matter how often we tried the above. For this one, we used a combination of Piers_A's advice in post 23 and killing WIA using Task Manager in post 148 by charles95722. Note that we were unable to ever stop or restart the WIA service correctly using the Services tool. This was a clue that something inside of WIA was broken, so I had to go further than Piers_A's steps and try charles95722's kill using Task Manager.
When we did the kill, Windows asked if we wanted to discard all the data of the running process, and we said yes. I think this was the key--something in the WIA service was stuck/corrupt, so no amount of stopping and restarting the WIA service by rebooting changed anything because it was saving the state between stops and starts. (Remember that stopping and restarting in Services did not work, so we had to "restart" WIA by rebooting.) As soon as we did the kill WIA by Task Manager, relying on the Recovery First Failure to restart WIA, the Scanner Properties test worked and everything else worked.
We will have to run this for a while to see how it holds up, but it seems to survive reboots just fine. We have no interest in unplugging and replugging USB cables, so we did not test that.
Note that we tried these steps on 6 or 7 PCs with Canon MF4690s attached, so the process is repeatable. We tried skipping steps like the reboots and unplugging the USB cable and did not have luck with those attempts, so they are probably necessary.
