Scan123 requires TWAIN compliant scanners in order to communicate correctly. Issues can occur if the incorrect driver is selected.
If you do not see your TWAIN Scanner Driver from the dropdown, it is because the correct Scanner Driver has not been installed yet on that machine, your scanner is not on, or there is an issue with the wired connection.
First, please check the connections between the Scanner and PC to make sure there are no loose connections.
If that does not resolve, then try switching the USB connection to a different USB Port on your computer and verify again. If still not being recognized, let's restart (not shutdown) your Scanner and PC and verify if it appears on the list after your computer has turned back on.
If the option is still not there, then the Scanner Driver is missing from your computer and needs to be downloaded and installed.
For Fujitsu fi Series Scanners (PaperStream IP):
(The download link is the middle link for PSIPTWAIN-2_10_3.exe):
http://imagescanner.fujitsu.com/global/dl/setup/psip-twain32-2103.html?MODEL=5141
For Epson:
Use the search option to input your model and then download the full driver
https://epson.com/Support/sl/s
For Canon:
Use the search option to input your model and then download the full driver
https://www.usa.canon.com/internet/portal/us/home/support/
For all other models/brands, please reach out to your IT to confirm the correct TWAIN Driver to download.
NOTE: If your computer does not have Admin permission to install programs or you are unfamiliar with the process to install programs. Please reach out to your IT for assistance.
After installation, please go to the Tools Menu > Settings > Scanner Dropdown > Select The new Scanner Driver that is available as your scanner.