Forum post Scanner won't add media notes thare are known problems with the scanner release distributed with server RC1. If you have not yet updated the scanner to the latest release available from the github distribution, try the update to see if that helps.
After installing the new version of the scanner delete the _media folder in the server folder before restarting the new version of the scanner. Observe the scanner window as it starts and check it shows a list of media files scanned.
You can also check if the scanner is seeing the media folder by using the http endpoint access. On the server machine use a browser with address line:
http://127.0.0.1:8000/CLS
which returns the list of audio, stills and movies stored in the scanner database.