I tried many online suggestions, none worked. The only effective one, finally, was one from 2012! For a Windows 11 (and probably 10) computer, add this to your path - C:\Windows\twain_32\MF4100 (or whatever is in the twain_32 subfolder for your device, although it's likely to be MF4100 - just look in that Windows twain_32 subfolder).
How to add something to your path in Windows?
- Press a Win key on your keyboard
- Type: env
- You should see something like this:
- Click on "Edit the system environment variables" (left or right one, it doesn't matter)
- You should see something like this, entitled System Properties:
- Click the Environment Variables button (bottom right)
- You'll see something like this, entitled Environment Variables, with a list of items under Variable. One is named Path, highlighted below (I've blanked out the rest):
- Click on Path. Then click the first Edit button just below its box (or, just doubleclick on Path)
- You'll see something like this, entitled Edit environment variables, with a list under it (again I've blanked out some info):
- Click on New, then type in or paste the path to the twain_32 MF4100 subfolder which, for me, was as above:
C:\Windows\twain_32\MF4100 - You'll see something like this, with the added info now at the bottom of the list on the left:
- Now, click OK and just keep clicking OK (I counted 3 times altogether clicking OK) till you come out of the Environmental Variables box
- For me, that was it! MF Toolbox then started working properly again, I didn't even need to restart my computer.
I hope this helps others, it's been driving me mad for months!