General Advice

1. Has the scanner lost its internal programming? Use the scanner test page if it is a keyboard wedge scanner.
2. Ensure USB cable plugged into correct port still. Switching the cable to a different USB port can cause a new and different COM port to be allocated. Plugging the cable into the correct USB port will solve this without any changes to software or pinpad.
3. Cable disconnected. Usually not a problem as scanners often derive power from the USB port, so if the cable is not connected the scanner has no power. Some scanners use batteries or seperate power supplies, so worth double checking

Rare Causes

1. Was the computer last rebooted 20+ days ago? (Check reboot time from C:\> systeminfo ) And the scanner is a keyboard wedge device (most are) and the Pos Version is less than P1869. Try rebooting the PC and the scanner may function again for few weeks. There is a fault fixed in P1869 where scans would no longer be recognised after several weeks of continuous operation. (NB Important you get a true reboot, not a suspend/hibernate/restart)