Your bar code scanner needs to be configured to act as a Keyboard Wedge and use STX as well as ETX.
The following image is from the scanners codes supplied by Honeywell for their Voyage/Eclipse range of Bar Code Scanners. Your bar code scanner should have come with similar codes printed in a manual or leaflet. If you have lost yours, you should be able to download and print them from the barcode reader's manufacturers web site.
Please take the 4 four steps as follows:
Configuration of your scanner should be almost identical to the above.
Restore Defaults
First restore your bar code scanner to it's factory defaults.