Was the DBV-200 working before and now it started acting up? Or has it never worked? If you set all of the DBV-200 dipswitches on the bottom of the DBV to OFF and it still runs continuously then you need to remove the DBV head to see if a bill or something is stuck back in the transport mechanism. Also you can open the top part of the DBV head and see if a bill is jammed in there.
On the back of the DBV-200 there is a gear that has to mesh with a gear on the transport, so make sure the DBV is installed correctly. That gear turns the transport mechanism gear to initialize the transport and set it back to its home position. If either gear is missing a tooth, or if the gears aren't turning together then that won't happen.
And make sure the cables that connect to the left and right side of the DBV are plugged in properly. The connectors have small pins, make sure none of them are bent over.
Also, you will need to better describe what is happening to get help. We can't see what you are seeing, we only have what you write.
Another suggestion, your questions will likely get more attention and more advice/suggestions if you post in the area on NLG that pertains to your particular slot machine since the setup & operation of the bill validator often depends on the machine it is installed in. That's where the experts on it usually hang out. If this is an S+ machine then here is that area:
http://newlifegames.com/nlg/index.php?board=80.0