Thanks so much for the information! Based on what you have explained, here are some steps to try:
1. Go to Start Menu. Type %temp% in the search bar and hit Enter.
2. Go into the following folders: “7z57d86”, then “OJ6500vE709_Full14”, then “Setup”, and “Scan”.
3. You will see a .msi program named “Scan”. Right-click on it and select Repair (it may ask you to restart the computer).
4. If it doesn't work, or gives an error, take note of the error. Then, right-click and select “uninstall”, and then “reinstall”.
I noticed there is a new “Twain_32” folder, according to you. Please ensure there is a “Twain_old” folder, then delete the “Twain_32” folder completely.
If that doesn't work, try these steps next, which is specifically to address the 1706 Error: Fatal Error 'Error 1706. No valid source could be found for .' (MSI Error 1706) Message Displays During Software Installation in Windows.
Please post your results.