I am trying to install and run a Canon CanoScan 4200F Scanner, and I have installed the software and have it connected. I keep getting a pop up that says - experiencing a twain problem - maybe scanner is not connected - which it is? Help
Twain is a software bridge between computer and scanner.
Reinstall the scanner, making sure you include the Canon Twain driver, preferably downloading it all afresh if you're currently using the stuff from the CD which came with the scanner. Also refer to the Canon manual.
If absolutely no joy, have a look at Silverfast or Vuescan third party scanning software which seem to work with everything.