Hello,
I think I may found a solution to MF Toolbox Problem. I realized that problem starts after Windows update.
System and device:
Windows 10 Pro 64 bit
Canon i-SENSYS MF4890dw (I think it's a European version imageCLASS)
Solutions I tried:
1. Reinstalling drivers (I downloaded newest from Canon website).
2. Reinstalling MF Toolbox (I downloaded newest from Canon website).
3. Installing Patch from european Canon site (it was proper for my device).
4. Added a path in system enviroment variable (found it on this forum).
5. Changed properties in WIA in Windows services (found it on this forum).
Nothing worked and I wanted to give up and start using Windows Scan App...
The solution that worked for me:
1. Press Windows button an type "update"
2. Go to Check for updates (Windows)
3. Go to "Update history" (just under the "Check for updates" button). Find the latest one that is not for Adobe player or other software - just something like "General update for Windows 10 systems Version 1607 based on CPU x64 (KB3200970)" - sorry for translation, I don't know how it is in english.
4. Go to "Uninstall updates" (at the top) - new window will pop up.
5. See updates group "Microsoft Windows" (in my case it was the lat one) and find the latest update (dates are at the right of the window).
6. The latest one that stands for "Security update for Windows" or "Update for Microsoft Windows" and has the same symbol e.g. "KB3200970" as you found in step 3 should be uninstaled. Just right clik and uninstal.
7. It will take a while, so be patient. After uninstaling, click yes to restart your computer.
8. After rebooting, probably the problem will persist. My computer downloaded the same update I just uninstalled and prompted me to reboot to install it again. After the update was installed again (during rebooting), my Toolbox started working! And I'm also able to use my device to scan directly to my computer.
I think it's the proper solution, because it worked twice for me (for the first time I thought that something else helped). Scaning problem with MF Toolbox probably will come back after next update, but I'll be prepared for that :-)